I suppose you could create one based on the average wage and the average cost of living. I’m sure something like that does exist. Buying power or disposable income or whatever.
GDP is useless because it counts things like all the money proles are forced to pay to their landlords. And the amount they fork over to energy and utility companies. It counts the hugely inflated value of property markets. It’s not very indicative of how us small folk actually live.