At the society-level UBI costs very little. It is wealth redistribution, but its not like the military where significant productive efforts are wasted with tax dollars and where the marginal return for taxpayers is extremely low. UBI money comes out of the rich primarily and goes into the poor, and economics have demonstrated pretty concisely that the poors consumerist goods spending is significantly more stimulating to the economy than a capitalists investment spending.

You can't really judge a states spending exclusively in tax dollars in, or you get where we are in the US with derelict infrastructure and understaffed hospitals, fire departments, and public schools. You are taxing money to spend it for a reason. As long as the results are worth the price paid (and infrastructure at least is enough of a force multiplier to give you a lot of overhead for corruption before it is inefficient) you aren't "spending a lot of money" because your economy is growing more than you shrink it by taxing it.

It is only effectively dead weight taxes (corruption, the military, modern foreign aid, politicians salaries, bureaucracy, insane overregulation) that is tax money wasted. And sure, a lot of it is wasted. Which is half the argument for UBI - the metrics are simple and should be transparent to prevent anyone corrupting what would be a force multiplier.