From [1], we already allocate roughly $6k per person per year in the US, enough to fork over $25k/year to the poorest 20%. (This doesn't account for the potential savings of reduced crime (prisons are expensive!), improved health/nutrition, reduced administrative overhead of replacing all welfare systems with a single basic income, etc.)

Also: not all value is neatly captured on a W-2 form. If turning my backyard into a decorative garden allows me to set a higher sale price for my home later, I've contributed. If I buy groceries so that I can play videogames all day without falling over from hunger, I've contributed. (If I can pay in cash instead of food stamps because I collect a basic income, even better: there's less bureaucracy on the way to collecting tax on my purchases from the grocery store.)

[2] notwithstanding, people who contribute literally nothing to the economy are extremely rare.

[1]: https://en.wikipedia.org/wiki/2015_United_States_federal_bud...

[2]: http://www.becomingminimalist.com/the-man-who-quit-money-an-...