You can see below how I cleaned my cassette with grocery store stuff like cooking oil and hand-cleaner. It worked very well but I used about 0.2-0.5 liter cooking oil, material cost perhaps 0.1-0.5EUR (but very dirty cassette and I think I could use less).
This brush was going to bin, reuse at the best. Cost = 0. The other side of the brush is hacked to clean some in-between parts, you need a knife for it, again cost = 0. I used also a braking cable to some parts.
I used a braking cable to get the dirt between the cogs and other places, worked well, needless to buy expensive Par.* plastic things.
Picture before final cleaning where it became like new but good comparison to new one. Sorry different products actually, the old cassette is done with dimmer metal and a bit heavier. On the surface, you can see the cooking oil.
Cleaning the cooking oil off can be a hurdle, you don't want it while riding because it will go rancid more here. If your hands stand or you have hand-protections, you may want to try cloth-cleaning-stuff, cheap bulk grocery store stuff. I have tried it and it is a bit more effective to hand-cleaner stuff to take the oil out, particularly with running hot water. But if you cannot take the cooking oil off, even with hand-cleaner, cloth-cleaner, running water and brushing, for some odd reason you may want to try the petroleum products suggested by this answer. I have never used petroleum products but they should work but maybe too expensive in your location.
Cooking oil has transformed the initial salty-dirty-bad-stuff to easier cooking-oil-mess. I am still uncertain to which extent the cooking oil can be bad to the chain particularly if left rancid, perhaps no worry at all if you can take the most of it out and perhaps it will go out when you ride some kms, anyway working well for me.