The big question when you put anything out into the open market, and probably the biggest conundrum facing any author, self-published or otherwise, how much will the book sell for. Being an Indie I can't hand it over to marketing to do the calculations for me, but I know that Mark Coker at Smashwords has given the subject considerable time and thought. He's posted on the Smashwords blog and at Slideshare a couple of presentations (here and here) based on his research into the dynamics of ebooks sales.
Both presentations are worth a look at, and provide considerable food for thought. There is no magic bullet that I can see but more helpfully a solid appraisal of the situation facing any writer in the market place today.
There are likely to be as many ways of selecting the price for a book as their are writers, but one or two common factors seem to pop out. Obviously free shifts more dowlnoads than anything else, about 92 times more than, and ebooks come in a variety of prices but there is a correlation of approximately 30000 words per dollar, putting a full length novel edging towards epic length, (70000 to 1000000 words) around the $2.99 tag.
Have a look at the presentations, and see what you think.