How much does a pcb like this cost for a small prototyping batch of 1 or 5 for example?
A simpler wired design like my E80-1800 (https://github.com/ebastler/E80-1800) can be completely assembled by jlc for ~30ish USD per unit.
Oddly enough, small-batch prototyping at jlc can be cheaper than medium sized (50-150 pc) runs at other fabs.
Hope this doesn't sound like an ad, I've compared a lot of prices and nobody came close to jlcpcb, but With their limitations (limited stock, limited finish/color choices, frequently chnaging stocks and component prices) and sometimes far-from-ideal QC (some scratches can happen, in rare cases even missing components that were present in the BOM) they are not really my first choice for production runs. For prototypes or small unofficial-ish batches with a few friends though - god tier.
It is actually very informative, I was very surprised to learn that one could get fully assembled prototypes for a few hundred bucks.
If you are going to hand-assemble a macropad or something, you end up paying more in shipping than you pay for a set of 5 PCBs.
Also, most factories allow you to calculate the price on their website! Look for PCBway, Elecrow, JLCPCB, OSH Park, or a dozen others.