[vetinari]

Taxes do not work linearly like you seem to think.

If you double the tax rate, you won't double the tax revenue. There's a big chance that the revenue would go down.

Another thing is, that money is not the wealth; productivity is. So if you want to pay UBI to everyone and want to keep the same purchase power of the dollar, you have to preserve productivity at the national level (GDP is a measure; but you need that specific physical output as products and services, not money). Which you won't, if a part of population would stop working.