^ Same for me. I sell about 20 print photos a month and my prices vary. It depends on whether:
a) who wants it (whether they are a friend, private individual or company);
b) why they want it (personal use, website, brochure, profit); and
c) how much they want (bulk/larger numbers always result in a discount).
For friends who just want a smaller image for a desktop screensaver, there's no charge.
For friends and casual users, I usually charge $5 for a 8x10 print, $10 for 11x17 and $20 for 13x19. 13x19 is the largest print I can generate on my printer - for 20x30, I send those out to be developed and charge a minimum of $50. This covers my ink and paper charges, with a little extra thrown in for my time and effort.
For companies, I usually charge double to triple the above prices.
However, I've sold as many as ten photos at a time to companies and provided decent discounts as a result, because they are buying in bulk. I've also had friends and family buy from 3 to 6 prints at a time to redecorate their homes, and I discount that as well. $140 to $200 usually ends up being the target price for this kind of a grouping.
Many commercial customers want only the digital images to develop, print or use on their own (e.g. I don't generate prints for them). For these purchases, the use and volume determines the cost.
I sell every year about eight images to an ad agency in San Diego who uses them for a real estate relo guide. Because of the volume and repeat customer (three years in a row now), I charge them a flat fee of $250.
For a local real estate company here in Phoenix (I do all of their corporate photoshoots, for example), I give them a steep discount on photos they buy from me. Usually runs about $400 a year for about 20 photos that they use intermittently and on their website.
Obviously, if I'm hired to take the photos and am paid for my time (rates start at $50 an hour and go up to about $100 per hour), I don't charge them for the images, as they belong to the customer.
I do all of the photography for my law school and they get a sweet $50 rate as a result of the volume they send my way. I usually bill them about $200 a month for a couple of photoshoots, and I've sold dozens of prints and other digital images to both students and staff, including $250 worth of photo prints for the mediation clinic. This has been a real gold mine for me.
For weddings (I average about one per month), I usually charge about $400 for a standard 2-hour shoot. They get their own prints, which is less hassle for me. I just post process a few of the best, burn everything to a custom printed CD and give that to them.
I also shoot about five real estate listings per month at $75 a pop. This usually takes about 15 minutes of actual shooting. They get about 20 photos, from which the realtor picks the six best for MLS.
Overall, I've been doing very well with photography, as I'm averaging about $1k per month with it. Perfect gig for someone as busy as I am in law school.
Hope this helps.
--don