When I first started out on Kindle, I priced my books at the lowest price available - 99 cents US. Some of my books did well and others didn't do so great.
Then I began to read up on the psychology of pricing and on pricing Kindle books. According to many other writers, their books sold better when they were priced higher.
I decided to experiment with my own pricing. I kicked my best selling book up to $2.99 US and held my breath. Amazingly, there wasn't a slow down in the sales. In fact, the opposite happened - I got more sales than before and instead of making only about 30 cents US per sale, I was making a touch over $2.00 US per sale.
I then began to up the prices of my other books. First I kicked them up to $1.99 and, after another month, I pulled them up to $2.99. For my latest book, I set the price at $3.99 and it is now my second highest selling book.
For the record, I do still have a few books priced at 99 cents - about one book for each pen name I write under so that readers can get a feel for my writing. The rest of my books are priced at $2.99 and above.
I guess the lesson I learned was to not cheapen my work. It is worth more than what I was charging for it and, after I raised the prices, readers also considered my work worth the price they paid.