Sony wouldn't make any money from the sale of used games. They might, however, lose money due to angering their customers.
I can't think of what they would hope to gain from doing something like this. Since they seem to be denying it, it's probably just a rumor that got out of hand.
I don't think I'll be buying a PS3 (without having to sell some organs on the black market), so none of this really matters much to me.