But on the positive side for single-payer healthcare, there's no upper bound on how much you get to consume, subject to medical necessity. The problem is that

But on the positive side for single-payer healthcare, there's no upper bound on how much you get to consume, subject to medical necessity. The problem is that medical problems are financially bimodal: they tend to be pretty cheap (take some antibiotics) or incredibly expensive (you need dialysis or you have a brain tumour). So unless you have some sort of useful insurance plan that covers people and minor dependents for less than what you're getting in basic income you'll end up with the problem of people who are unable to get serious medical conditions treated. And making medical treatments universally accessible is part of the point of most single-payer healthcare systems.