The A 70-210 is also very sharp and capable. I sold my A 135 2.8 because I thought the zoom was better than the prime. I've since bought a Takumar Bayonet 135 2.8 in case I need the low light capability, and the Takumar seems a bit better than the SMC-A wide open - but that one was much cheaper since it's not SMC. I've also looked into getting the M 200 f4 but everything I read makes me believe that the zoom can keep its own against that prime as well, and at f4 the zoom might be sharper (the 200 f4 is said to be a bit soft wide open, sharpening up at f5.6 - the A 70-210, at least my copy, is already very sharp and contrasty at 200 f4).
Looking at KEH prices - 3 A 70-210s in EX condition ranging from 39-69 dollars. They have 3 EX/EX+ A 35-105s for 149 to 175 dollars. Even their bargains are twice as expensive as the 70-210 EX... Adorama has two A 70-210 that would probably fall under "bargain" by KEH and they are 15 and 25 dollars each. The prices for this zoom have steadily fallen since I came to Pentax.
Don't believe the A 70-210 is sharp wide open at 200 f4? It gets sharper by f5.6, but at f4 it's already sharp enough. These are all wide open: