They should raise the price back up of course. There will always be people who will buy the game for full price, because they don't care. I mean look at Intel. The performance difference between their flagship and their second fastest processor is about 2-5%, as it has always been. Yet, as always, they charge over $1000 for their flagship, while they charge $400 for their next in line. With the performance difference so minute, you wouldn't expect those $1000 processors to sell as well as they do, but many people are wealthy enough to not care.
Selling L4D at $25 had a greater psychological impact because it was a 50% reduction in price.
As for the question in general... are games too expensive?
Well, if you compare buying a game to going to a movie, and look at it purely in terms of hours, you might think games are more than fairly priced. You pay what, $10 for a 2 hour movie? At the same time, there is a LOT more unique entertainment in a good 2 hour movie experience, than there is in most two hour portions of a game.
Sure you can enjoy a two hour playing session of Bioshock at any time, but most of it isn't as unique as a movie; there isn't nearly as much happening constantly. And if you look at a game like Halo, at least the single player aspect of it has a lot of monotonous portions.
So are games overpriced? I think so. But it is difficult to compare it to the movie going experience. While a game can in theory provide endless periods of entertainment, how many gamers even finish games? While watching a great movie only provides entertainment for a couple of hours, the quality of that entertainment can be far more exhilarating.
Taking Portal for example, which I really liked, and thought it was worth $10. If I had a choice -- pay $10 for six two eight hours of Portal, or pay $10 to watch The Dark Knight, or Transformers in the theaters with my friends... I'd most definitely watch the movie.
Still, it is a difficult question, because there are plenty of other factors. Do games cost more to make than movies? Also, games with free quality multiplayer experiences can be very valuable.
I think something like the original Unreal Tournament was outstanding in terms of the hours of quality entertainment it provided.