As I was talking on the Grimoire thread, it should go through all of those. Allow me to rant a bit:
"Early adopters" are the consumers that want it hot and fast, and are willing to pay to dollar for it. Think on those guys on Apple store lines, just waiting to buy the new iWhatever (or MHC on Steam), they know they are paying more than most will pay in a few months, but they wanna own/play it now, while it's new, the hype is flowing or he just was looking foward to it for a long time. IMHO, 15$ is a good price for most of the good indies.
After 1-2 months, start the promotions. People willing to pay full price already did so, now you have to target those who were waiting for a discount, lower prices or more info/reviews/Konsensus on the game. $9.99 should work well, it's a good price, still single-digit and "feels" small. If you did a Kickstarter, to avoid backers getting pissed at you selling your game so quickly at "backers price", you should still make it a bit higher, like $9,99 if you asked for $8 on KS.
After 6-8 months, talk about your game has probably disapeared, so you should do a nice price drop and perhaps add a little free content to roll the ball again and even get some newspost on some forums/websites "Game A releases big patch/free DLC & lowers price". Here you should go 7-5$, depending on how sales are and what you intend to do next.
Few indie developers seem to understand this (KotC and Frayed Knight guys included), but if you're making a sequel/DLC/expansion, expanding your community is crucial. Is what Valve does masterfully, they give free heads for people to buy hats for them! You don't have to
give them, but selling the game for 4,99 or even lower will ensure that WAY more people will know who you are/what you're selling when you appear with a new, full-priced product. And again, you can sneak in some nice newposts, something like "Game 2 release date announced, Game 1 now for 4,99!" that will help both your products.
Anyway, that's a quick view of what I think on the subject, one must never underestimate the power of low prices, ESPECIALLY with digital goods. You don't have any cost for each copy, profits for selling 10 games at $20 or 100 at $2 are the same, and you'll find the later way easier to achieve after a while.
And yes, I think that >15$ is too much for a indie game...