Well, I've never had any luck at all at Thrift shops, but I've managed OK at flea markets. Between myself and a mate, over the last year we've managed Canonets, Ricohs, Voigtlander Vitos, a Contaflex, couple of nice Zeiss folders, Minolta Himatic, Olympus Trips. Nothing spectacular, but a raft of usable stuff for between $5 and $40.
Best pickups for me have been my (perfectly working) Weston Master II meter for $10, and a 1949 "Using the Leica" book for $25....
I still dream of finding someone selling "Grandad's old camera, it's been sitting in a box for years" for next to nothing, and finding a mint Leica IIIg. So far, it hasn't happened... 🙁
tim