UBI isn't black hole spending like the military. A lot of money is moving through the fed in taxes but that money isn't going into a black hole or having a huge inefficiency quotient taken out of it, the vast majority of UBI checks will be immediately spent and recirculated without any overhead.
It is undeniably true that the majority of UBI checks will be spent as "fast money".
Nevertheless, the money is going to come from somewhere and that somewhere is taxes. It would be unreasonable to not calculate the total sum of taxes required for various levels of UBI funding, IMO.
It depends on how you phrase it. If you treat it like an expense, people will balk at the proposal as unreasonable. And while a lot of tax revenue ends up being wasted and becomes effectively an expense, 6 trillion taxed to maintain a $1500/month UBI for all adults is not going to slow the economy the way 500Bn for the military does. At worst, the wealthy are getting a fraction of their tax money back in their UBI check and putting it right back where the tax revenue came from - investment accounts.
It is the same way infrastructure investment works. Nobody wants to do it because the upfront bill looks big. But the decades long projection of efficiency of most high-demand projects would eclipse the cost by an order of magnitude. Meanwhile special interests (mainly those who would not immediately benefit from the infrastructure themselves) keep phrasing the conversation around "how much it will cost" these projects never get done, and the national economy suffers as a whole for it.
