We can, and do, but the ‘ow much?! Crowd don’t help.
Unfortunately those of us that know and appreciate how much work goes on to actually make a part vs those who only look at the cost of a lump of material is a very poor ratio.
If I could use an example, said maker I mentioned before charged me £35 for 3 bits of turned down 15mm ID aluminium to make me some 15mm adaptors for my Hope XC hubs. How much?? Well if you consider the material cost, the machine cost, energy cost, other bullshit costs like rent, lighting, insurance, accounting and business infrastructure (website etc) built into each item BEFORE you even consider paying the person who did it for their time, I think I got a pretty good deal.
I could do that myself, I’ve done machining and I’m actually pretty decent at it however I have neither the tooling, room or funds to do it so I have to accept that anything I want is a single item commission and pay accordingly. Even then, I’d need to either do a lot or be turning some pretty specialist stuff to make it even close to worth it financially (I’m pretty sure mistakes would also be made along the way).
This is where the split between hobby and business happens. With the former it’s easy to just enjoy it and only charge for material costs. With the latter it’s a whole other ballgame and a matter of putting bread on the table or not. Look at Burf and ‘Cindy’ from BTR as an example of what happens when shit goes south.