Originally, I sold mine for $4.95 but I decided to change it to free after about three days post release. I received my Artist Royalty and found out I sold 2. I probably could have sold a few more, but I decided most people would prefer it free.
It all really depends on the product you have and how much the true value is. If you are looking to release something, I would recommend a 0.99 cents price tag. Anyone can afford it and if it's not a good product, the reviews won't be harsh.
I've sold 147 copies of Restored, so far. That's not as many as some people though, I know one person who's sold over double what I have. I won't name him because sale figures are a personal thing but he might comment on this thread.