Hi Kate,
Thanks for your question relating to wholesale and retail pricing.
There is another way to work out the best pricing for your prints and that is starting with how much you feel customers would pay and doing some market research by asking the question to people who you feel would be your key customers. Once you have this range of pricing information you can then work backwards.
The other way to look at it is cost price plus a mark up say 25% and then a percentage of margin on top of that which can also give you a buffer to adjust your pricing and mark downs etc for slow stock without loosing money.
Hope these two insights help you