The Trek 412 I bought for $20. I stripped the paint, primered and painted it, cleaned and lubed the BB and headset, dished the rear wheel, and flipped and chopped the drops. It's pretty clean now.
The total cost $65: $16 for cheapie cog, $8 SRAM chain, $5 for chainring from Ebay (obsolete BCD), $0 for BB lockring from my converted Miyata, $11 for primer, paint, and clearcoat, $5 for new toe straps. Saddle and fenders I already had from another bike.

It's a 52cm with a 54cm top tube, just a tad big for me but feels OK since the stem is shortish. I may sell it or keep it for a rain bike. We'll see how it rides first.