It will depend on the situation how much you would spend on luxury goods.
Living in China, if you have a car, a house, more than 10,000RMB cash you can use, then you are rich.
I don't know, it is complicated, is like I heard once: money doesn't bring happiness but leaves you feel sorrow in Paris or inside a ferrari. We need some money to survive, the problem is turn a slave, the greed will destroy us.
I love the old Roman definition: Enough to buy and take care of a horse on your property.
Is it true? Not really. But wealth is so comparative...
Living in the USA, I'd say that you are rich if you can pay for a child to go through whichever university they want without worrying terribly about where the money will come from.
richness is not in money it's in heart :::::::::::::