In the days when the character was created I don't think football players made all that much - especially unsung ones like the offensive line.
Google Fu says the average NFL salary in 1970 was 23K, with the rookie base of 9K and a veteran minimum of 10K. That is the first year that the player's union was able to get such a contract. The Blob first appeared in 1964.
Salaries didn't even get to those levels until the end of the AFL, as before they came into prominence there wasn't enough competition to create the bidding war which led to the merger.