"Will I miss it if I don't have it?"

That's the minimalist question. You only buy something if the answer to that question is yes. 

Of course, you can answer yes with a straight-face even when you ask yourself that question about a Ferrari. 

But most people wouldn't. 

How many purchases that you make (with your time and your money) that have an answer to the question as a yes indicates how close you are to being a minimalist on the spectrum from minimalist to maximalist. 

Whereas, how many objects / experiences that you answer yes to (whether you end up purchasing them or not) indicates where you are on the spectrum from stoic (where you answer yes to only the most basic ones) to libertine (where you answer yes to practically everything).

Where we fall on this grid determines how much money is enough to have a happy and fulfilling life.