Originally posted by Rondec Nikon has cheap lenses and then they have expensive lenses and very little in between. As to how good/bad a deal Pentax is depends on what you compare lenses to. If you compare the FA 77 to the Nikon 85 f1.4 it looks like a good deal. If you compare it to the 85 f1.8, not so much.
I assume with the slower primes (50f1.8 versus the 50 f1.4 and 85 f1.8 versus 85 f1.4) that biggest differences are in the rendering of out of focus areas and micro contrast, as the slower primes seem to have decent sharpness, even wide open.
I'm a kind of micro-contrast addict, and in spite of what many say, I haven't found micro-contrast to be easily produced in PP programs. Pentax lenses (ltds., but also Takumars, and K's, and M's) have good to excellent micro-contrast. I haven't had a Nikon camera, but from the pics I've seen online it seems you have to pay
a lot to get similar micro-contrast in Nikonia. (It is my subjective impression that the general Pentax rendering is quite a bit nicer than the rendering of Canikon, and that micro-contrast is what makes this difference.)