I'm trying to hide my wealth from my family (parents and siblings), but I want to buy extravagant things. What should I do?

I’m not sure if hiding is the right word. I think they already know I make good money. But I pretend to be frugal, so that I don't have to give them any money. They aren't poor, but they don't have much money. And I really have no interest in sharing with them. No moral lessons/lectures please.