// Unless I’m misunderstanding this you’re also giving it to people who don’t need it.//
This is true *initially*, but this point was addressed in, for example, the first link in my answer at 17:36. It's a lot to get through, and since it takes the form of a transcript it can be tricky to follow, but boils down to people who earn (significantly) more than the UBI rate simply having their UBI taxed right back, in effect paying it to themselves: "take $6 out of your wallet and put those $6 back in", as Widerquist has it.
Depending presumably on where this effect kicks in exactly, this lowers the cost to something like 3% of GDP for most large economies like the UK. Bearing in mind that spending on the current welfare state is around 10% of our current GDP, then even if that 3% turns out to be an underestimate it could still end up representing a net reduction in cost.
These are somewhat back-of-the-envelope figures, and I again want to stress my point from earlier, that "the exact cost depends on how you organise the scheme", which applies equally to the suggestion above that you *save* money by introducing UBI. Still, taking a given UBI rate and multiplying that by the adult population, and quoting that figure as an argument against the scheme, is completely misleading.