LMAO i remember the FD7 (sold them actually)
I too would regret having traded an M6 for one of those (though at the time they sure seemed a technical marvel)
Best deal on primes if you don't mind manual focus is to hit the boot sales and buy the old ones. I picked up an SMC M 50 f1.7 in portobello last fall for 10 pounds, so pretty much pass on a couple of pints and it's paid for
my most used primes have cost me a total of $100 CDN (about 60 pounds) a 28 f3.5, 50 f1.7, 100 f2.8 200 f4.0
that's one of the beauties of Pentax complete backwards compatability