Are good pentax lenses this scarce?
I don't know. All I do know is that I put 11 Pentax lenses on Ebay (the M and A series ones that I find I don't use since I bought FA series replacements) and 7 out of 11 were sold within 48 hours at sensible BIN pricing.
Whatever Pentax relevance or not to 'state of the art DSLRs', there is a very healthy marketplace for Pentax gear.
Godfrey