The reality of the matter is that publishers will get a cut of every sale on Steam, whereas they lose a lot of volume on xbox to used games. The publisher compensates this loss of sales by charging a higher price and/or not discounting as frequently. Used game sales are 100% profit to brick and mortar stores, so any attempt by xbox live to reduce prices beyond an infrequent sale will just result in the stores undercutting them.
No,
here's the reality of the matter:
1) Every game ever sold used was at one point sold new, thus the publisher did in fact receive money for it.
2) If used games did not exist, not all of these same people would rush out to buy the game new. In fact, many of them wouldn't buy the game
at all, as used games are often a great way for people to test the waters in a franchise they haven't played before. Few folks buy a brand new $60 in a franchise they're not sure they'll like. The notion that every used sale directly steals a new sale from the publisher's wallet is a faulty presumption.
3) The frequency of discounts have nothing to do with used games. Never have, never will. There are sales all the time at stores, and in many bigger stores, games are thrown into the bargain bins the moment they stop selling. If publishers have frequent sales, the stores will "undercut" them, eh? That's hogwash.