I only buy physical copies of albums on vinyl, since I don't have anything to play CDs with on a regular basis (and CDs are kind of a rip-off anyway) so here are my rules for how much I'll usually pay for an album -
If it's something I kind of want, and there's probably a billion copies out there and it might not be my only chance at all, but it seems like a good idea at the time: No more than $5 if it's in great condition; no more than $2 if it's kind of beat up in some way or another.
If it's something I've been searching for in the past few months and it's in really nice condition or a considerably rare find: No more than $10.
If it's an album that I consider a missing piece to my collection/an absolute must, terrific find, excellent condition: No more than $20.
Picture discs/limited collectible editions (with a rating of VG+ or better): No more than $30.
Keep in mind that I refuse to reduce myself to picking up s
hitty vinyl. I don't like scuffed/scratched records at all. I've put a lot of love, time, and money into my collection.