philcore, that *could* work, but now you're really basically luxury taxing everything that isn't deemed "essential, so now you really are penalizing for purchasing - if that's the government's only source of income (or did I misunderstand?) those taxes would need to be huge.
Those who are more fiscally foresightful would have more money for investments and savings, but purchasing beyond the essential is basically being discouraged. I don't know what grand economic consequences it might have, but I'm betting they aren't good it seems to me that jobs will be lost since you're reducing demand, and the overall joy (if not quality) of most people's lives will be reduced as people can't afford their little luxuries.
So, the poor are basically reduced to a completely luxury-free subsistence living because that X box now costs $1500.00.
The middle class is royally shafted, since they are the ones with the highest disposable income to "nonessential purchasing" ratio, and they WILL keep buying stuff - but are paying more for the same amount of stuff.
The rich aren't hurt, maybe even helped, since they're now being taxed on what they buy, instead of what they earn. Even though they're probably coming out ahead, they still don't buy as much, because they're frugal.
I see economic meltdown if you don't tweak it a bit.