The average American might make 60k; the average person makes more like 2. The billionaire also doesn’t have an income of a billion a year, he has an accumulated net worth of a billion. Median wealth is measured in thousands of dollars. And the numbers on the left half of that distribution are very low indeed.
But anyway, whether it’s a billion times more or merely a million times more, the difference is still staggeringly huge.
If you have a dollar, how many more do you need to make a billion? About a billion.
If you have a million dollars, how many more do you need to make a billion? About a billion.
The average person has $60k-ish a year. There is nobody out there with 60 trillion.
Regardless, the billionaire has to actually spend the money to get goods and services from the market. While his/her needs will dwarf an individual, they are still just a drop in the bucket compared to the middle class. This is why all of the largest companies/product markets/etc all cater to the middle class.
The only way billionaires can actually get leverage on how society is run is through direct monetary influence of politicians, but that’s going to happen whether the average income is $60k or $200k.