People tend to value things based on what they paid for the product. If you sell a print for $100.00 that is its value..if someone else sells ao similar print for more or less than you did that becomes the worth in people's mind of the second print. I believe there are, for instance, people who would not buy a Merecedes or BMW if it were selling for the price of a Chevy. If you give someone a free print then the person getting the gift may well think that it is worth next to nothing.
Of course none of this helps you in oricing your prints it is just my thoughts about attitudes.