Pricing is a strange thing in the digital world, whether you're talking traditionally published or indie books. The per-book costs are negligible, so you don't have to start with a baseline of printing + distribution for anything beyond the initial expenses. Thomas & Mercer, for example is talking about leaving the price for The Righteous at $2.99 or $3.99 and then pricing the subsequent books at $7.99. This is cheaper than a paperback, but significantly higher than what indies typically charge.
The two prices I see for the vast majority of indies are 99 cents and 2.99. I don't want to debate the 99 cent price because that has been rehashed a million times. The argument against 99 cents is that it is just a gamble to try to climb the rankings and that it undervalues all the work involved in writing a novel. There is some truth to both of these arguments, and yet I've used the 99 cent model myself on several occasions. Both The Devil's Deep and The Righteous have sold thousands of copies at this price.
But what about the subsequent books in a series? I don't see any reason why they should be $2.99. If someone likes the first book enough to seek out the second, will they balk at $3.99 or $4.99 or even $7.99? Maybe, but I'm guessing not. If a writer is hoping to make a living at writing, there is surely a point on the pricing spectrum that is the sweet spot between giving away one's work and getting greedy? My goal is to offer my work at a fair price, but not to undervalue it.
And so my current price point is $3.99. Of my thrillers I've got three books at that price right now, two books at $2.99 and three books at $.99. I'm planning to raise the price of Implant and State of Siege from $.99 and $2.99 to $3.99 as soon as I release the audio versions on podiobooks.com. That would leave all of my books either at an introductory price for a series of $.99 or at $3.99.