Could you allow your teen to go without lunches if he bought these?

Hypothetically, let’s say a thirteen year old boy came into $500 and he was expected to buy his lunches with it and anything else he wanted. After three months he had $250 left and blew that on a pair of headphones without permission. Would you “cover” for them by giving him $250 for school lunches , ground him or how would you handle it if the $500 did not come from you. In other words, it was given to him with no strings attached by another source other than his parents with the exception that he had to buy school lunches with part of it.