Upload & Sell: On
bought a 20mm f3.5 nikkor for $100 a few weeks ago. Had to be the ebay snipe of the week, but if you keep looking, you'll find something in that price range. I got a 24 f2.8 a few years go for under $80, a bit worn, but great optics.
If you want REALLY cheap, look for old Tokina 24mm prime lenses. I had one in the 80s and it was really nice, until I dropped it. Should find one of those for under $50.
If you want cheap but great IQ, you need to consider Rokinon/Samyang 35mm or 24mm, but those really aren't "cheap" in my world view of money and its value.