Interesting discussion going on over here:
Indie games should be cheaper
I follow the Zeboyd guys on Twitter and their school of thought is, can't be too low as you leave yourself very little to discount as well as perceived shovelware. If you price yourself to high, people (who are used to sales) will just wait for a sale. And if they are just going to wait for a sale, then they are going to forget about your game.
And if the first sale comes and you remember it, maybe you can wait longer until the next sale or possibly when it gets bundled.
In 2008, if anything ever reached $5, I insta-bought it. Today though, insta-buying is now at $1.
Insta-buy = don't think or look at reviews, just buy it.
Basically the only games that I *really* want to play, I'll go and buy it. But I'll go to places like Nuuvem or GMG instead of the Steam store. Which to me says they should discount it via the humble widget. Humble only takes 5% so they could say, "Hey our game costs $20, but $5 of those dollars goes to Valve. Instead buy from our site for $16.
Don't know if Steam allows that for individual devs as opposed to authorized resellers though.