In a balanced UBI, the UBI is paid for with taxes. So if you make the average income, you get $X from UBI and your taxes go up by $X. If you make more than average, like your example, then you pay out more than you receive in UBI.
Because average income is considerably higher than median income, most people benefit from UBI.
(I hate saying trillions of taxes when talking about UBI. Since most of the effect of the increased taxes is just a clawback, on net the tax is only in the hundreds of billions).
Morally, there's also a good case for taxing income for UBI -- it's a fair claw back for those that don't need UBI.
But there's a solid base to your argument -- we definitely should be increasing other taxes and decreasing income taxes in general.
Even stimulus checks that were small and arrived irregularly had a huge impact on hunger in America. $1000/mo on the regular would be revolutionary.
In the case of rent in particular, there would be no reason for any landlord to take less than $UBI if there was a guaranteed monthly payment from the government.
Unexpected or unpredictable cash influx almost always makes things better because people know they can’t “count on it” and they use it for savings or to fix problems they had been unable to fix, rather than “live off it.”
To put that differently: what most people really need is margin to handle the unexpected problems in life. But living below your means to create margin is hard, even for high-income people! Doubly hard when you are low income. So unexpected cash is more beneficial than expected cash, precisely because it is unexpected and therefore inherently “margin.”
Some fraction of people will reduce their workload so their earnings are $3000/month, bringing their total income back to $4000.
Some fraction of people will not reduce their workload at all and inflate their lifestyle to depend on $5000/month.
The overwhelming majority of people will choose the latter; we already know this, it's one of the chief complaints about a materialist, consumerist oriented society. When people get a raise, they overwhelmingly spend it. It's why most people can't save a $1000 emergency fund.
If you are earning $2000 per month and suddenly your income increases by 50% you feel like a baller, you are going to start eating better, ordering take out a little bit, replace that cracked phone, add a little more data to your cell phone plan, turn that thermostat up a little, whatever.