As far as I know, people act as if they're math dorks, even if they don't make those explicit calculations (the same way your average basketball player doesn't know that f = ma, but can still apply f sufficient to give a particular m the a necessary to make a three-pointer).
For most people, the increase in utility from $75k to $100k is negligible
Well, the savings rate is not variable enough by income for that to be true. It looks like people ratchet up their consumption nearly as fast as their income increases, so it is fairly linear. And if you consider utility to be the optimal bundle of goods, even rapidly diminishing marginal utility doesn't change the fact that you get exponentially more consumption bundles with more money, so the best bundle is likely to require a high income.
I still think that talking about the final outcome is not useful, since the final outcome is hidden behind the probability of failure. You can't talk about the incentive to play the lottery just by reciting the prizes -- the odds are important, too.