In a UBI situation demand would shift, not just go up. If there's two hypothetical people paying the tax, a very rich person (>300.000 a year) and a poor person (<50.000 a yr), money effectively shifts from the rich person to the poor person (at least the majority). The poor person will have very different demands than the rich person.
Finally, we already do price controls and subsidies in many places, like food production. It's just that a big part of the advantage is soaked up by big companies.
Finally, we already do price controls and subsidies in many places, like food production. It's just that a big part of the advantage is soaked up by big companies.