Kathie here is an Australian example for you:
A shopping centre kids photo chain tooks some pictures of my son and when the proofs came back they wanted to charge me $70 AUS for an 8x10. There were lots and lots of people there paying these prices. Of course, I didnt, cause I knew I could take the same photo myself and get it printed at a professional Lab for $3.50 AUS.
When I do weddings for friends, I dont really charge for the work (although I should), but if they want prints, I usually charge about $20.00 for 8x10 (for example).
I think you need to look at the printer you would use, look at their pricing, factor in postage or work out if you are going to charge that to the customer on top, think about how long it takes to edit the pictures to the correct size and prepare them for going to the printer and then add on a profit margin for yourself that you are happy with. Remember it is your art and your expertise that people are paying for, so you are quite within your rights to have a decent mark up on it.
I would charge a sitting fee based on the time for the sitting and the time it take to edit the photos from that sitting, but remember that you can make good profit from the prints, so dont go overboard there.
Look at other photographers websites too, cause they often have pricing and package deals on their websites.
I realise I'm a bit late posting, and I might not be any help at all.
