We do. Plenty of them. If you want references, one place to start is with an intermediate text on public finance.
There is data on incomes by income class and many other characteristics reported by the Census. There is research on non-monetary types of income received by the poor. There are measures before taxes, after taxes, and after taxes-minus-transfers. There are various measures of income inequality.
I'd be surprised to find an introductory text which does not make clear the distinction between GDP and well-being, or between GDP and the condition of the poor. The use of GDP in political debate as a welfare indicator is another matter, but this thread is getting ridiculous.
mbs