At least in Indonesia it is.
At least in Indonesia it is.
Economics of scale.
For instance, when a bike manufacturer buys thousands of groupsets directly from a component manufacturer, they get a significantly better per unit price than a retailer can.
The retailer not only must necessarily buy in lower volume, but also typically buys through one or more layers of middlemen, each layer adding their cut to the wholesale price.
Thus, the typical replacement price for a single part is often double or more than the original cost to install it at the manufacturer of the bike.
In addition to economies of scale, you also have to consider the difference in price sensitivity and leverage between a manufacturer and a consumer.
If Shimano told Trek that they'd start paying retail prices for their cranks, for example, your next Trek would have SRAM cranks. You can be sure they've negotiated the lowest plausible price, because it's very worth it for them to make sure they buy a component for $34 instead of $35 when they're selling thousands of bikes.
Consumer-level parts purchases, however, generally fall into upgrades (you want an Ultegra shifter) and replacements (your shifter broke so you need a new shifter). The first group is generally price-insensitive practically by definition, since no one really needs an upgraded derailer, and you can get away with charging them more for the privilege. The second group is also going to be less price-sensitive by virtue of the fact that their cost to get their bike working again with a single component is always going to be lower than the price of buying a new bike.
Component incompatibility makes both of these more important. If you want to replace a Shimano derailer, it's generally very difficult to determine which non-Shimano components will work, so you're "locked in" to a given manufacturer. From this we should predict that known-interchangeable parts (handlebars, cranks, etc) should have lower markup than their counterparts, but I'm not sure how to measure that.
Prices of goods are pretty much unrelated to the cost to make them, they are set at the maximum value company can get away with.
Parts are generally sold for repairs, not new bike construction.
If you already have a perfectly fine 95% of the bike, your two options are spend a lot to get a whole new bike, or a little to get a new component. Even if the component costs twice what it should, you're still saving 90% compared to buying a whole new bike.
It is an economic law that the value (=cost) increases if you split something in smaller parts. Examples:
This might be related to the physics principle of entropy. The separate parts (tomatoes, apartments) may be sold to different customers that have different needs, where the entire system (box, building) can only be sold to one customer that has the specific need for the entire system, which limits the number of potential customers.
As for the bicycle, as a whole it can be used for only one purpose / customer. When sold as parts, each part may be used independently for a repair, for building a custom designed bike, etc. More use options means more value.
The mere fact that selling parts separately involves more handling costs is not a sufficient explanation. If separate parts do not have a higher value for the customer(s), it will be difficult to recover the higher handling costs.