Do you mean it took 60-80 man years to get the Unreal engine to where it is today? Any chance you could find the source for that or site you think you saw it on?
"man years" is one of many statistics used to sound really impressive even if it's not portraying anything impressive, because the number scales so well. "60 man years" is conceptually a long time, but it can just as easily be one person working 60 years or 30 people working two years (which, from that PoV, isn't a tremendously large project).
My favorite joke about the issue:
Q: What's IBM's definition of a "man year?"
A: 730 employees trying to get a job done before lunch.
That was to develop one of their iterations, it was a team of 20 working for three or four years. I can't find the source, it may well have been a talk at GDC.
My favorite joke about the issue:
Q: What's IBM's definition of a "man year?"
A: 730 employees trying to get a job done before lunch.