This is besides the question, but in game theoretical terms, an iterated version of the game would promote more equality.  If we're going to play repeatedly, I (proposer) know that you have a rational reason to veto an "unfair" proposal --that is, so I'll learn to be fairer next time.  So I'll probably offer a more equal split to begin with.

In a one-shot game, there is never any purely financial incentive to reject whatever offer.  As I said, not even a 5000$/0$ one.