as high street retailers threatened to stop selling the games if steam/others undercut their price
lol, thats like a cow protesting a new fast food chain by eating itself.
im pretty sure steam simply charge so much because they can. people will pay it, due to the convenience (i like knowing my fav game, morrowind, will always be readily available to me, no matter how many new PCs i go thru).
but stuff is only worth what people are willing to pay. and valve know this all too well.