Means testing has been shown to cost significantly more. That’s why I’m a fan of universal programs and not welfare programs (like the one in this study).
I would argue someone making six figures getting 10% more will have a big impact still. Give everyone the benefit, even billionaires. Using your argument, the billionaire won’t care about getting an extra $1,000 - that’s nothing to them. But no one feels “cheated” because you arbitrarily put the limit, and you know no one else is cheating the system because there is no system to cheat!
Paying for universal programs would require changing our tax structure, which I’m also supportive of.