I don't know why this would be unbelievable or "whopping." $3.3M over 60 years of adult life (age 20 to 80) is $55k/year. That's pretty close to the median American income.
I don't think it's very common to work until you are 80 years old though. Also, is the 55K$ figure after taxes?
And the median household income is actually $75k now. I'm just saying that $55k is very much in the ballpark for the median person. Does it really matter if that's before or after taxes?