It might be bad economics for steam in the long run. They are building a brand expectation that almost every game will hit the $10 price point that they stock, and the long term is that more people (myself being my main example) now plan to wait out purchases until they hit the systemic lows 3 - 4 years after release. I got Neverwinter Nights 2 for $5 over the sale, for example, after having bought the first one back in 2003.
I mean, there is a natural trend of the cost of games towards $0 since the cost of reproduction is so low (thus the rampant piracy) and it seems Steam has proven that exponentially more people buy games at half the retail price outright.
I think if they just launched games at $30 rather than $60 on Steam, they would have significantly more profits just because a lot of people that pirate new releases due to the insane $60 price point would buy the $30 one, along with a lot of people like myself who wait on the blockbusters to go on sale. For example, Witcher 2. I'm waiting for it to go below $10 (also, waiting on my new gaming rig this summer) because I know it will eventually go that low. If it launched at $30, I might have bought it back in March.