You just need to move to a MUCH lower COL area with better jobs...
Also, who in the US is paying half of all their money to taxes? It's probably more like 30-35% total, possibly even less depending on the amount of pre-tax retirement space available to him (government job w 403b+457b vs private job w 401k + CBP vs nada).
Even if the total effective tax rate for said person was 35% on an income of 350K, that is only 122k, leaving 227K behind. Lives off 100K, saves 127k/year with good returns (let's be generous with 10%) that gives you $2.2M after 10 years.
I'm going to assume said individual made and saved more than the above suggested numbers.