Giving $500/mo to everyone would cost like half of the current federal budget per year.
But the final argument for something like this is: do you want to thrive while someone else starves? Would it not be worth it to you to thrive a small amount less in order to ensure that nobody is starving?
I mean, inflating away debts is certainly one way to reduce the associated pain, but inflation can also wipe out wages, so it’s a bit of a balance. We haven’t seen a permanent UBI scheme in a large enough way to know what might happen.