$20,000 in 1900 is worth $619,971.43 today, so not sure what your argument is. It's not the raw number value that matters but what people can buy with it.
The average annual salary in 1900 was in the range of $450. That's about $14k today. What's worse, that when norms dictated a ~60 hour week and households, even at the low end of the spectrum, were often single earner.
While "rich" is over stating it, based on purely inflationary measures $20k in 2020 (or $645 in 1900) was not bad pay.
