I have had prints up for sale only a few times. This is what the place charged (in inches, and U.S. dollars, unmounted and unframed, signed limited edition prints)"
Prints on 5x7 paper: $60
...8x10 paper: $100
...11x14 paper: $200
...16x20 paper: $500
...20x24 paper: $800
Remember that galleries take a huge chunk of this (40% where I have put stuff up), so the prices are "high" in my book.
I sold three color 20x24s (a one-off series of three related images for $2,000), and the entire limited edition of five black and white 15x15s, at two separate shows. (Kept the wall display print for mahself, and it is on my wall.) Strangely enough, when I put up smaller (AKA cheaper) prints of the work that I really consider to be my best at a third show, not one sold. Lots of compliments, but no sales. All 35mm hand held stuff; journalistic, diaristic, road travel, street, nightclubs, etc. Guess it is the kind of stuff that is fun to look at, but not something you would want on your wall. This sort of stuff I am going to start putting into books instead. Gallery walls are not where it belongs, IMO. Bad decision putting it up, but they offered the space and that is what I had been working on, so up it went. People love that IMO pretty unimpressive large-scale fine art shit that many people can do well, but have little love for the really great and difficult to make journalistic shots.