I think they charge $60 because they've found the market is willing to pay $60. Price is one of those things that's hard to calculate (the Price is Right gameshow proves you can't instinctively know the price of anything). So they start there, which really means companies start around $30 per game with the rest going to distribution and retailers. We're so used to those price points that we don't challenge them. And they represent good value for money compared to other entertainment medium.
Direct digital then is a much more attractive offer for developers - you can cut prices and increase profits. I think the future is buy on demand, accessing new levels and such - that's pretty obvious these days. In an entertainment saturated market it's more important to get players to play your game first, so I can see a time where you buy the first couple of levels and then buy the rest - removing the block of having to pay alot up front (which others have mentioned is a factor in deciding to buy physical games). Hell, I think the subscription model will eventually take hold where you pay $10 a month to access every EA game including new releases (unless consumers are will to pay more, which they probably are).
Gamestop have 4000 stores in the US. They're closing the 150 worst, but I expect more to close over the next few years. Like PC World, Radioshack, Comp USA, Circuit City and so on, retailers in the tech space are on deaths door. At a certain point in loss of business the company just isn't viable any more. Someone mentioned high speed internet as a barrier that necessitated brick and mortar, but we're already talking about the PC and console owning households - I doubt very many of them don't have internet already. Hell, Netflix is in more homes than cable. And as for big games, you don't download everything before you start playing. The imports can be drip fed over the course of the game.
Here's the path for physical retail sales. They've fallen in half in 7 years. Gamestop is going the way of Blockbuster, and I don't know if their diversification play will prevent that. If they continue on this current rate you'll see very little retail sales in 5 years, and what there is will have to be thru big box retailers who themselves might cut their investments in video games like they've done for DVD's.