US Senators make $193,400 per year and there are 100 of them. This ~20mil doesn't exactly stack up to the ~1.8 trillion of US government discretionary spending (or ~4 trillion of 'mandatory' spending).

the salaries are the least expensive part of their cost.

It doesn't really as our minds can't truly comprehend the population or volume of goods sold. Without that it's meaningless.

excellent point. but it's a start