This is the standard adventuring ideal, right?
So, let's say you play a lawful/good type who routinely returns the cash orcs steal from caravans, kings, whoever. Isn't this person, in essence 'spending' the money with their choice to return it to some random, previous miser, as opposed to exchanging it to a new, different, miser?
Why shouldn't they get XP for returned loot, if that's their standard way of doing things 'right'? Imagine you give back Wave, Whelm or Blackrazor (if you don't know what I'm talking about, it's a good thing you can't see my eyeroll) to the previous owners, without threats or pursued collectors? If that's how you roll, you could get the experience of returning the item. Well, i'd give it to you.
What would a post like this be without a likely ignored suggestion for how to fix the problem?
rule variant idea: the GM attributes a general party alignment. If the party is neutral, don't bother. Otherwise, multiply rewards by one of three general options based on the party actions: .75 (opposite), 1(neutral purposes) or 1.25(with alignment).
Counter-argument: that would totally eff my campaign's own moral compass, Gary sez, I won't even dignify this with a reply, etc.. Yeah, yeah, I hear that. To this I say: