If you publish through Amazon.com, be aware of their right to change your pricing at any time. BUT, if you sign with them at $2.99, you will receive the 70% royalty rate, even if they drop your book to $0.99 (compared to the 35% rate that you sign for at $0.99/book in the beginning). This article is fascinating. Take the time to read the comments section as well.  Who Controls Your Amazon E-book Price? by Jim C. Hines.