PP —

You are right that providing a UBI to the rich increases the cost of the program relative to UBI’s close cousin, the negative income tax. However, that effect can be substantially mitigated by imposing a “double dipping” rule under which those with high income don’t get both the UBI and existing income support like Social Security. The UBI should also replace “reverse welfare” benefits like housing deductions and subsidies to retirement benefits. For details see https://medium.com/basic-income/how-much-basic-income-can-we-afford-52cc8e9da65 . (I like the fact that Yang follows this principle; not all UBI advocates do this.)

I don’t get your point that “above a certain income level UBI provides no incentive to work.” Clearly, the disincentive effect (income effect) of a UBI is even weaker for those with low incomes than those with high incomes, and because of high earnings from extra hours worked, the substitution effect is stronger for the rich. The effect of high earnings at the margin is what causes high earners to work longer (not shorter) hours. See https://www.nber.org/digest/jul06/w11895.html