"upper class" means whatever people use it to mean, hopefully something that's useful to the discussion at hand.

NFL players get paid very high salaries, but the average career is only three years. many of them blow through it and have only meager pensions and the aftermath of injuries to look forward to in their old age. are they "upper class" for the brief part of their life when they have the cash flow or just an edge case of the exploited worker?