I'm right across the street from an art gallery who sells some of my prints. It of course varies on size, but I have some 5x7 black and white matte finish prints that are mounted and matted to 8x10 selling for $35 each.
When I price my artwork, I take all my direct costs (film, printing, modeling fees, MUA fees, etc) and multiply that by 5 and that's where I start selling it. If I'm going to print no more than 25, then I do all that math for 25 prints and sell it at that cost. It makes a little more sense to sread $500 of model/MUA fees over 25 prints versus 1.
If it doesn't sell, I bring the price down. If it starts to move like hotcakes, I raise my prices. I usually introduce them in increments of five. I also sign each one and number it as well.
Of course what that print is worth is really only what that guy is willing to pay for it, but this is the formula that works for me.