I like the site, not into collecting things of any sort myself but I have to admit that stamps are pretty darned cool.
I'm not going to rehash all the fine points stated above although I heartily agree with the fact that you are probably selling them for too low a price.
My suggestions are as follows:
- Package stamps and sell the packages. Otherwise you are going to have people buying all the great ones and leaving you with the less valuable ones. If you package together valuable one and less valuable ones (although themed) you can move both kinds at once.
- Not sure what you are using for the individual stamp shopping cart but (if you have time) it might be worthwhile to include more detailed descriptions for the search engines to use (e.g. Columbia - 10 cent stamp - 1959 - Mint).
- I'd make at least one more price point for the more valuable ones, maybe 3 instead of 1. I'd rather sell 50% less product and make 50% more money.
Did you take all the photos of the stamps yourself? You could try putting them on the stock photography websites to make a few bucks from that as well (you've already done a lot of the work).