If you're talking about the high-end ED Pentax glass or the legendary lenses like the SMC-A macros, K-mount prices have always been correspondingly higher than Nikon or Canon gear. Pentax 35mm use among pros peaked with the Spotmatic and screw mount lenses of the 1960's and has been losing market share almost ever since. Exotic Pentax lenses are relatively rarer than Nikon or Canon, even though the ordinary K-mount lenses were sold in vast quantities.
The 200mm SMCP-A* f/4 Macro is one such lens, often selling these days for north of $2K when they come up, which is perhaps once or twice a year. They were extremely rare even when new in 1988, too-- something like only 4 had ever been imported into the USA, I was told by a Pentax regional rep back then. Catalog price in the day was, IIRC ~$750. But just try finding one. The non-ED 100mm SMCP-A f/2.8 Macro commonly sells well used for two to three times what I bought mine for in Mint condition two decades ago (at $250, it's been one of my top money-making lenses through the years.)
That said, of the better "ordinary" primes, the Pentax SMC-A 50mm f/1.4's can be found on eBay all day long selling for right around $100 and will hold it's own with normal primes of any make or model. The build quality and smoothness of the focusing helix is second to none. The manual focus 24's are equally fine and commonly found for $200 at auction.
The bigger question may be finding a manual Pentax body that still works. Most all 25-30 year old LX's will have the infamous sticky mirror issue by now if they haven't had recent service. The Motordrive LXs that still function are few indeed. The PZ-1s were reasonably good bodies but not pro level gear as they had no dust sealing and 3.5fps motordrives. Pentax dropped the ball on bringing out an LX replacement, IMO. Nikon F5s and Canon F1s are now flood the market and may represent a better bargain, even though they're each nearly half the weight of an Abrams tank.
Pentax did have quite a following among pros for its medium format bodies. The 645N and NII take not only all the Pentax 645 lenses, but with an adapter all the P67 lenses with full open-aperture metering function . There are also a number of ED teles available. These bodies and lenses are plentiful and cheap and among the best values to be found anywhere in photography just now.
