Sorry people but money has f*ck all to do with it

Example?

Dempsey v Carpentier 1921 Dempsey was paid $162,000 and Carpentier was paid £105,000 (so the huge purses have been there for nearly a century.
Ali was raking in multi millions per fight in the 70's too!

Put that into todays terms and it's serious money (even by today's standards).

They simply fought more in those days,sometimes as much as 30 times a year and there weren't silly amounts of weight divisions and belts with different sanctioning bodies etc.
they fought more so were in better shape and always fighting fit which means on the whole they were tougher by far imo.