Those who suggest that custom luthiers should adhere to the traditional model of Supply & Demand may be neglecting the operative word here:
"custom"
Small, bespoke, boutique manufacturers operate by their own rules. They probably didn't go into business to play the Econ 101 game, they got into luthiery to satisfy their muse ...and then mercifully figured out that they could sell a few of their babies.
iow, expanding production (by hiring employees) is not an option; they're not interested in running a company, they're interested in building musical instruments.
Likewise, raising prices only accomplishes one thing (if that)...presumably demand will go down if the price gets high enough. At least that's the theory. But, being primarily individuals, some small bespoke, boutique luthiers actually have a vested interest in maintaining the perceived value of their product...which may mean not raising their prices, but simply accepting that yes, there will be a long wait for my instruments, I hope customers are patient. (I don't know for certain of any bass builders who subscribe to this approach, but I'm aware of at least 2 or 3 of the country's most respected handbuilt bicycle frame builders who do, so it wouldn't surprise me at all to learn that there are luthiers who share that attitude.)