There is no reason to expect "buy stuff you want" to be more charitable than charity. At a glance, the stuff itself obviously takes up a good chunk of the money and much is going to end up in the hands of people who already have plenty.

You emphasize "sustainably", but how is it more sustainable to give 500k/year to capitalism until you don't make that much / retire / die? In either option, that 500k/year is there until it isn't. With charity, you'd help more people but it would be no more or less sustainable.