The below was my summary of other answers.

I've now had my bike for 10 years and can answer from experience -- my bike is a "Kona Dr. Dew" which cost $700-$800 (when new in 2010) -- which I ride at most about 7,000 km per year.

It's aluminium with hydraulic disk brakes and maintenance is minimal:

• I have aftermarket "Marathon Plus" tires, which never flat and want replacing after 5 years (though it's been 5 years since they were last replaced and they don't seem to need it again yet, maybe the first set wore more quickly for environmental reasons, e.g. standing outside in summer sunlight or winter sub-zero).
• The chain and brake pads seem to need replacing once or twice a year -- more specifically about every 3000 km. Or the brake pads wear less quickly if you're not cycling on hills, or in city traffic (frequent braking due to traffic lights etc). After installing the new chain they check the derailleurs' adjustment.
• They often replace the cassette when they replace the chain, but I recently bought a chain gauge, so I'll see whether replacing the chain as soon as it needs it will make the cassette last longer. I think they also replaced the triple chainrings once.
• They replaced the bottom bracket after about 30,000 km, when the crankarms began to wobble a bit. The bike shop recommended a good (higher-end than the original) second-hand bottom bracket which they had in stock, so far so good.
• The only maintenance I do myself is top up the tire pressure when I can feel they're not tip-top, and add lube to the chain occasionally.

That's all! They never serviced the wheels, nor the hydraulic fluid in the brake lines.

So it's been a real pleasure. Maintenance is fairly regular, but only to replace "consumables" i.e. the chain and brake pads.

Perhaps its frame being aluminium (not steel or carbon), and no suspension, and hydraulic disk brakes, and robust (rather than "aero") 700x32 wheels, help make it low-maintenance.

This phrase from the original answer below seems quite wrong in practice (so I want to correct it):

Cost of thrice-yearly service, and new parts (pads, chain, and cassette) might be $600/year (or more if you don't do your own weekly chain cleaning, and monthly brake and gear adjustments).

Instead iirc the LBS charges $50 or $100 to replace the chain and the maybe the brake pads, so the yearly cost seems more like a bit more than $100.

#Chains

There's a lot of information here about why chains wear, how long they might last, how to tell when they need replacing, and what happens if you don't when they need it.

• 1000 km (cross-country, or all-weather abuse)
• 3-5000 km (well-maintained derailer chains)
• more than 6,000 km for perfectly groomed high-quality chains, single-gear, or hub-gear chains (preferably with a full cover chain guard)

So if you're doing 800 km/month, then you ought to replace chains maybe monthly if you don't clean and lube them every week, otherwise 2-3 times/year.

#Cassettes

There are some conversations here, here, and here about how often a cassette (i.e. rear derailleur sprockets) might need replacing.

The consensus there seems to be that a cassette must be changed approximately once for every 2 to 5 chains; and depending on how expensive the cassette is, if you're using a relatively expensive cassette then change the chains more often (to protect the cassette from being abused by a worn chain).

Other estimates suggested 10-20,000 km for a cassette.

So if you're changing the chains 2-3 times/year then expect to change the cassette once/year?

And a cassette costs maybe $80 for the part (excluding labour; if it needs changing, the LBS will probably change it when they change the chain).

#Maintenance schedule

How much maintenance (not just what type of maintenance, but how much) does a cheaper bike require?

Don't get a bike that's too cheap (a 'BSO'): no amount of tuning will be enough.

A maintenance schedule will include:

• Clean the chain weekly (otherwise, at 40 km/day, expect to replace it and maybe the cassette every month or two).

• Check the tire pressures weekly.

• Adjust the brakes and gears monthly (either yourself, or at a bike store)

• Change tires whenever necessary

• Have an in-store tune-up 2 or 3 times a year: during which they may change the chain, cassette, brake pads, and tires.

Cost of thrice-yearly service, and new parts (pads, chain, and cassette) might be $600/year (or more if you don't do your own weekly chain cleaning, and monthly brake and gear adjustments).

And/or, how much longer will more expensive components last?

An internal-geared hub should be adjusted/serviced once, after it's installed.

A 7-speed internal-geared hub from Shimano might last 3 years or so, and cost $500 to replace; it's grease-filled.

An internal-geared hub from Rohloff lasts indefinitely, but costs $1700+ to buy; it's filled with oil instead of grease (change the oil once a year).

With an internal-geared hub (unlike with derailleurs) you can fit a chain-guard around the chain: in which case the chain might last twice as long, and want cleaning every two months instead of every week.

If you have rim brakes instead of disk brakes, then you may need to replace the rims (i.e. the wheels) every two years or so. Mechanical disc are cheaper to own than hydraulic disc

Chains

There's a lot of information here about why chains wear, how long they might last, how to tell when they need replacing, and what happens if you don't when they need it.

• 1000 km (cross-country, or all-weather abuse)
• 3-5000 km (well-maintained derailer chains)
• more than 6,000 km for perfectly groomed high-quality chains, single-gear, or hub-gear chains (preferably with a full cover chain guard)

So if you're doing 800 km/month, then you ought to replace chains maybe monthly if you don't clean and lube them every week, otherwise 2-3 times/year.

Cassettes

There are some conversations here, here, and here about how often a cassette (i.e. rear derailleur sprockets) might need replacing.

The consensus there seems to be that a cassette must be changed approximately once for every 2 to 5 chains; and depending on how expensive the cassette is, if you're using a relatively expensive cassette then change the chains more often (to protect the cassette from being abused by a worn chain).

Other estimates suggested 10-20,000 km for a cassette.

So if you're changing the chains 2-3 times/year then expect to change the cassette once/year?

And a cassette costs maybe $80 for the part (excluding labour; if it needs changing, the LBS will probably change it when they change the chain).

Maintenance schedule

How much maintenance (not just what type of maintenance, but how much) does a cheaper bike require?

Don't get a bike that's too cheap (a 'BSO'): no amount of tuning will be enough.

A maintenance schedule will include:

• Clean the chain weekly (otherwise, at 40 km/day, expect to replace it and maybe the cassette every month or two).

• Check the tire pressures weekly.

• Adjust the brakes and gears monthly (either yourself, or at a bike store)

• Change tires whenever necessary

• Have an in-store tune-up 2 or 3 times a year: during which they may change the chain, cassette, brake pads, and tires.

Cost of thrice-yearly service, and new parts (pads, chain, and cassette) might be $600/year (or more if you don't do your own weekly chain cleaning, and monthly brake and gear adjustments).

And/or, how much longer will more expensive components last?

An internal-geared hub should be adjusted/serviced once, after it's installed.

A 7-speed internal-geared hub from Shimano might last 3 years or so, and cost $500 to replace; it's grease-filled.

An internal-geared hub from Rohloff lasts indefinitely, but costs $1700+ to buy; it's filled with oil instead of grease (change the oil once a year).

With an internal-geared hub (unlike with derailleurs) you can fit a chain-guard around the chain: in which case the chain might last twice as long, and want cleaning every two months instead of every week.

If you have rim brakes instead of disk brakes, then you may need to replace the rims (i.e. the wheels) every two years or so. Mechanical disc are cheaper to own than hydraulic disc

#Chains

There's a lot of information here about why chains wear, how long they might last, how to tell when they need replacing, and what happens if you don't when they need it.

• 1000 km (cross-country, or all-weather abuse)
• 3-5000 km (well-maintained derailer chains)
• more than 6,000 km for perfectly groomed high-quality chains, single-gear, or hub-gear chains (preferably with a full cover chain guard)

So if you're doing 800 km/month, then you ought to replace chains maybe monthly if you don't clean and lube them every week, otherwise 2-3 times/year.

#Cassettes

There are some conversations here, here, and here about how often a cassette (i.e. rear derailleur sprockets) might need replacing.

The consensus there seems to be that a cassette must be changed approximately once for every 2 to 5 chains; and depending on how expensive the cassette is, if you're using a relatively expensive cassette then change the chains more often (to protect the cassette from being abused by a worn chain).

Other estimates suggested 10-20,000 km for a cassette.

So if you're changing the chains 2-3 times/year then expect to change the cassette once/year?

And a cassette costs maybe $80 for the part (excluding labour; if it needs changing, the LBS will probably change it when they change the chain).

#Chains

There's a lot of information here about why chains wear, how long they might last, how to tell when they need replacing, and what happens if you don't when they need it.

• 1000 km (cross-country, or all-weather abuse)
• 3-5000 km (well-maintained derailer chains)
• more than 6,000 km for perfectly groomed high-quality chains, single-gear, or hub-gear chains (preferably with a full cover chain guard)

So if you're doing 800 km/month, then you ought to replace chains maybe monthly if you don't clean and lube them every week, otherwise 2-3 times/year.

#Cassettes

There are some conversations here, here, and here about how often a cassette (i.e. rear derailleur sprockets) might need replacing.

The consensus there seems to be that a cassette must be changed approximately once for every 2 to 5 chains; and depending on how expensive the cassette is, if you're using a relatively expensive cassette then change the chains more often (to protect the cassette from being abused by a worn chain).

Other estimates suggested 10-20,000 km for a cassette.

So if you're changing the chains 2-3 times/year then expect to change the cassette once/year?

And a cassette costs maybe $80 for the part (excluding labour; if it needs changing, the LBS will probably change it when they change the chain).

#Maintenance schedule

How much maintenance (not just what type of maintenance, but how much) does a cheaper bike require?

Don't get a bike that's too cheap (a 'BSO'): no amount of tuning will be enough.

A maintenance schedule will include:

• Clean the chain weekly (otherwise, at 40 km/day, expect to replace it and maybe the cassette every month or two).

• Check the tire pressures weekly.

• Adjust the brakes and gears monthly (either yourself, or at a bike store)

• Change tires whenever necessary

• Have an in-store tune-up 2 or 3 times a year: during which they may change the chain, cassette, brake pads, and tires.

Cost of thrice-yearly service, and new parts (pads, chain, and cassette) might be $600/year (or more if you don't do your own weekly chain cleaning, and monthly brake and gear adjustments).

And/or, how much longer will more expensive components last?

An internal-geared hub should be adjusted/serviced once, after it's installed.

A 7-speed internal-geared hub from Shimano might last 3 years or so, and cost $500 to replace; it's grease-filled.

An internal-geared hub from Rohloff lasts indefinitely, but costs $1700+ to buy; it's filled with oil instead of grease (change the oil once a year).

With an internal-geared hub (unlike with derailleurs) you can fit a chain-guard around the chain: in which case the chain might last twice as long, and want cleaning every two months instead of every week.

If you have rim brakes instead of disk brakes, then you may need to replace the rims (i.e. the wheels) every two years or so. Mechanical disc are cheaper to own than hydraulic disc