Doing rough math, $500M isn't that bad...
At current wand prices (~$63) and Butterbeer priced at $8.49... they would theoretically need to sell 761 wands a day and 10,488 Butterbeers a day during a 10-year "payback period" (essentially just split the $500M between them both into a 65/35 split)... and this excludes all other forms of revenue/merchandise Potter generates.
Well aware there are operating costs, etc. I'm just putting into perspective that $500M isn't as bad as it sounds lol