Earlier quoted context omitted.
It's not really proportional, which is why it hurts the most. Wealthy people (who don't buy extravagant things) have most of the same basic expenses as the poor, and the sales tax can really be seen as a regressive income tax that eats up a larger portion of the income of the poor.
And the flat tax proposal is the same.
> There has never really been a compelling scheme for a flat tax that solves the problem inherent to it