Nah not on his first contract. He needs to take it all and build generational wealth. Just like Brady did. Then on his next contract he can give a break.
Note Brady didnt win any Superbowls while being paid near the top of the league.
Read what you just wrote.
Now consider that for an elite QB, there is much more money to be made doing commercials than in your salary. If he gives a hometown discount, knowing that he will make more off the field, he can allow the team to pay its players while demonstrating that he is willing to not be so greedy to the rest of the team, making them more willing to also give hometown discounts.
Using your own words, Mahomes will have more chances of winning Super Bowls if he gives discounts on his contract. More victories and Super Bowl victories, more money made from ads.
I will give you an example. Tom Brady made 15 million in salary in 2018 while making 12 million from endorsements. Well, that wasn't more than his salary. Did I mention that Brady was ranked 81st among athletes in endorsements? He basically didn't care to do many endorsements.
If Mahomes is smart, he can easily be making from 12 to 20 million a year in endorsements, allowing him to accept a hometown discount.