Dropbox could definitely have my business there and be price competitive if they offered say 250 gigs for under $100 a year.
Amazon S3 (some consider it wholesale) would cost you 3 times that, and that's not even considering in/out bandwidth charges or Dropbox's nifty client and version history (which lets you, for instance, restore "deleted" files).
The question is not whether dropbox is overcharging (I am quite happy to concede they are not) compared to some other service. The point is purely made from the user end. When I can own outright a 1TB drive for $99, what is the psychological price point for which I am willing to pay not to maintain it? Twice as much, sure. Three times, okay it hurts but maybe. Eight times? Asbolutely not.
All I am saying is adoption will rise if the price point drops. Right now it is high enough to turn off price-sensitive individuals.
Amazon S3 (some consider it wholesale) would cost you 3 times that, and that's not even considering in/out bandwidth charges or Dropbox's nifty client and version history (which lets you, for instance, restore "deleted" files).