The median US salary for an individual is 30k per year (median family income is 50k). So with an Amazon job an essentially unskilled worker can make more than half of all other Americans.
So, at Amazon's entry level, you're making 85% of the median personal income, plus benefits. And that's for their lowest paid FT employees, it can only go up from there. Where's the problem exactly?
fwiw, your numbers are correct, but the 30k figure includes part time workers and is therefore skewed to the downside. Among full time workers, the median annual income is about $51k for men and $48k for women, according to data collected by the BLS.
Median family income is ~86k. [0]
Median household income, which is likely what you wanted to cite and is the more common measure, is still much more than 50k, at ~68k. [1]
Median personal income is about 36k. [2]
Median hourly wage is $20.17. [3]
So, no, a $15/hr Amazon worker isn’t making above-median wage and, even if they work 40hr weeks for a full year, isn’t making above-median income.
[0] https://fred.stlouisfed.org/series/MEFAINUSA646N (nb: “family” for this purpose is defined basically as a household of two or more related by blood, marriage, and/or adoption.)
[1] https://fred.stlouisfed.org/series/MEHOINUSA672N
[2] https://fred.stlouisfed.org/release/tables?rid=249&eid=25956...
[3] https://www.bls.gov/oes/current/oes_nat.htm#00-0000