> If you argue it's unfair that people pay for UBI, how is that different from arguing that it's unfair that people pay for means-tested social security (or poor people's medical bills)?

There's a big difference between a welfare state designed as a form of social insurance to protect people from adverse circumstances and old age, and one designed on the assumption that those who want to work owe those who don't a living, and that the only circumstance that should affect how much people receive is whether they have the right citizenship.

Aside from the fundamental ethical rationale changing from contribution based social insurance to citizenship based entitlement, UBI would also represent a much larger bill, and a lower payout to the neediest.