I think these are the best way to give someone cash (if you want to aggravate them slightly). Graduation is typically a cash event so why not make them work hard for the money?
Once you put the money inside they have to complete the puzzle to get the cash!
MagNif Money maze Puzzle $7.99
Pinball Money Maze $9.34
If that looks like too much why not just an Amazon gift card?
As always this is Amazon- the price could change at any moment!