i'm having trouble finding the actual stats atm, but i'm p sure the stats describe something more like a logarithmic progression—in particular, i think you get super-diminishing returns on additional wealth after the 70k/year mark, but i don't think it ever actually goes negative.

but the extra gains aren't super-significant after a point, and coupled with personal preference (i.e. not wanting to deal people after yr monies) your point still stands :P