Why should it be better over $300k though? Thats a tiny tiny percentage of the population who very likely already has more money than they would need for the rest of their lives if they wuit working today, reguardless of age.

People should not be allowed to hoard wealth like that.

This graph should be savings early on, which still benefit those people, because, as you mentioned, it adds them up, but at some point, it gets worse.

Incentivise "spread the wealth". Lift everyone up, because by 300k, you are good, let others get more.