If you think that is a stupid idea then what is the threshold with a lower amount that this becomes a smart idea?
What evidence is there that whatever threshold you come up with is less stupid than my $100k a month?
We already meet people's basic survival needs because it's cheaper to feed your neighbor than make it impossible for him to raid your fridge. Not taking that basic gift away if your neighbor becomes self-reliant is just removing a disincentive to becoming self-reliant.
It is all very complicated.
The idea is to replace the complication with a simpler UBI in as close to a cost neutral manner as possible.
Taking money from healthcare and putting it in my pocket so I have to pay for it myself doesn't bring me much income you know.