Ultimately the market will dictate especially for unknown author self-publishers. Oftentimes first time writers charge the same amount for their books as best selling authors until they realize they are not selling many books!
Amazon allows self-published authors to modify their pricing anytime they want. Having said that many first time authors join to the Kindle Select program and offer their books as (free) downloads for up to 5 promotional days in a 90 day period. You just need to be signed up with one of those sites that send out email alerts concerning free books available on Kindle.
There are lots of ebooks sold in the .99 cents to $3.99 range. I sell my own for $4.95 however it's a lot lower than most books sold in the dating/relationship self-help genre offered by bestselling or self-published authors.