Hedonism is the pursuit of physical pleasure as the primary purpose in life

That’s a very narrow interpretation of one out of many types of hedonism

That’s like saying “religion is when you like Easter” 🙄

Billionaires are a good example of this

No they’re not. Billionaires are pathological money hoarders. Hoarding ≠ hedonism.

They get their kicks from watching their bank account go up and acquiring new things. But their brains quickly adapt to the new “normal”, and then they need a higher number or newer thing. It’s never enough.

That’s addiction you’re describing. Another thing that doesn’t equal hedonism.