I haven't sold a thing. Personally, I think these stamps are worth more, as attention and care equals "great product".
Right now, I charge by details. My most expensive are: the Twilight set, and that's because...I spent over 8 hours on these. The smaller pieces are cheaper because they take much less time to carve.
The Twilight set:
I'm thinking of creating and selling a set of Harry Potter house crest stamps. (That's Hufflepuff, Ravenclaw, Slytherin, Gyrffindor in one set.) How much should I charge then? (It usually takes me a couple of days to make these...)
Also, my packaging is of concern. I imprint the image on a piece of paper, and then shove it into a small polybag (like for extra buttons). Does this exude a professional feel, or not?