Here's some of my cheapies. Keep in mind my camera is a 2008 K20D, also a cheapie.
Auto Sears 50mm 1.7, 28 dollars + shipping on Ebay. I could have gotten it for even less had I been more patient, but this one looked like it had never been used.
SMC Pentax-K 55mm f2, 23 dollars for a Bargain condition one at KEH. I can't find anything wrong with it other than it looks like it's been used before. This is wide open:
Ricoh Rikenon XR 50mm 1.4, 35 dollars shipped because it looks very used, and has a bent filter ring (still useable). This is at f2:
SMC Pentax-M 50 1.7. This lens needs no introduction. I paid 30 dollars for mine here at the forum because it looks pretty rough and the barrel has writings carved on. WIth reverse ring:
Auto Sears 50mm f2. I didn't need this but couldn't pass on it for 10 dollars. My surprise lens - sometimes I compare my 50s when I'm bored and this one always takes the sharpest pictures. Colors are pretty neutral, not as nice as SMC but very natural looking.
Now let's move on to other FLs... this is my SMC-A 135mm 2.8. My most valuable lens other than the DA 35 2.4 which was really a splurge for me! But I got it as part of a film camera deal so it cost me next to nothing. This is wide open at 2.8:
My Tokina 19-35 is my 3rd most valuable lens. Worth about 100 bucks, I paid 90 for it in EX+ condition from KEH during one of their 10% off sales.
My Ricoh Rikenon XR 28mm 2.8 cost me 30 dollars shipped in like new condition. A few weeks ago I dropped it from pretty high on asphalt and bent the filter ring and the focus ring. I was able to unbend both to where I can use it again, but it looks so ugly now
on the positive side, the optics were completely unaffected, still sharp edge to edge. Try that with a modern plastic lens! This is wide open at MFD shooting some pebbles - it focuses close enough to be pretty much fun.
I have no favorites but I baby this one - my SMC-A 70-210mm f4 Macro. I bought it along with the 135 2.8 and a couple others with a film camera, so it cost me almost nothing. They can be had for 50-80 dollars all the time.
So that's what, a bit over a couple hundred bucks in lenses... and every single one of them works on full frame so I can use (and have used some of) them on my film camera. Solid build, great IQ, the weakest link is still me.