Steam has for me drastically lowered the value of a game, because while it is ONE thing to see game slowly decrease in price over a number of years, it is another to find prices slashed to 1/4 of the price seemingly at random.
What difference does it make what the price of the game is? The re-sale value of the game is zero because (as far as I know?) one cannot sell or even give away Steam games after purchase.
As an owner of a bunch of used games (both PC and console), I think that's too bad.