How to handle friends who "never have money"?

my best friend never has any money for anything. I know how much he makes and he makes more than I do, but if we are ever out he doesn't have more than a dollar on him. I always give in and buy his food but I'm not sure how I feel about it. It gets old after awhile. It's payday and mysteriously he is already out of cash (he gives his money to his wife who apparently handles the famalies finances) What gets me is that when it's time for vacation, they have plenty of money, they also always have a brand new car in the driveway. I don't want to ruin our friendship but I can't keep doing this! Should I have a talk with his wife or what? what you think?