Look I've returned 2 wallets I found, & even though they both gave rewards (one a bottle of wine, the other girl just gave me the money that was in it), relative speaking the token rewards gave me no satisfaction (even though they were nice & I appreciated them), compare with the satisfaction I got from doing the right thing & making someones day.
But to be perfectly honest, I'm not sure how I'd react if there was a hell of a lot of money in either wallet.
In the situation of a wallet with money but no Id, you can always drop it in to the local police station & if it isnt claimed within a month (or whatever the certified time is), its yours. I did that with a camera I found & ended up with a nice 35mm job with a zoom lens. If you want to be a bit sleazy, you could always hand it in at a police station 30 mins away on the train in a suburb on the otherside of town. The odds are then that it will never be claimed, & the coppers won't bother pursing the matter either. (just tell them you found it in the spot you found it, but you were running late for some apointment in this area & tell them its inconvenient to return to the area you found the item as its out of the way, that way your not lying about where you found it. I know a pick pocket that use to go through this routine & by doing that, the items he pinched became legally his, well unless someone can prove he pinched them).
But doing crap like that only has a short term gain factor, while doing the right thing will make you feel good for much longer.