Even the median income comparison is probably too favourable - Wuhan and LA are apples to oranges. I'm sure LA is one of the higher-income cities in the US, and Wuhan is one of the lower.
LA actually isn't super high. Median income is only about 2/3rds of the real top cities (DC suburbs have a median of almost $100k, LA is more like $60)
That probably doesn't accurately reflect the income difference between LA and Wuhan. Large parts of China are still effectively the third world. Urbanites in America make more than rural folks, but the difference is less drastic.
You're right, they make "only" 7x as much.
US Median Income: $43,585 China M.I.: $6,180
http://worldpopulationreview.com/countries/median-income-by-...