Do they actually believe in supply-side economics? Or is that just a rhetorical cover for cutting the taxes their donors want cut?
See also a couple of pertinent John Kenneth Galbraith quotations:
The Republican War on Economics
Even the most liberal Republican denies basic economics.
I'm on the 'economics deniers' side of this. They actively disregard facts that contradict their wishes.
They're feeling rich because the president is their fellow republican.