I mean, on the one hand, 100m for three fights is pretty goddamn awesome. On the other, if it means he misses out on more, I can see why he is upset. It's a good PR move by Hearn because it can either make his fighter make more money, or make Wilder look greedy.
A while ago there was a study that paired people off. Person A was given contril of 10k and could determine the % split between themself and person B. The only move person B had was to either accept what they were given, or veto, in ehich case nobody got anything.
Interestingly enough, while there were a few that were grateful for what they could get, they were outliers. Most of the "person B's" rejected absurd splits not out of greed but out of the human awareness of fairness. We sometimes forget that, even in a shitty world with tainted taco meat and Martin Shkreli, people have not abandoned their notions about fairness.