Why even insist on that $12K number in the first place, isn't that like approaching the problem from the wrong end?
It's something that always puzzled me about economic policymaking, regardless of which country; Changes seem to happen at a pace of years and only with static values, which makes reacting to our modern volatile and interconnected markets, in any useful way, impossible.
Case in point the basic income: Ideally the amount of money people get could be linked to the general living costs, adjusted to their area of residence, and some national economic index.
Sure the first one could be abused by people registering in more expensive areas while living in cheaper ones, but in the long run, and economic big picture this would only lead to rising prices (and basic income) in the cheaper areas, generated through the spending by the "cheaters".
Imho something really underestimated is how much of an economic boost a basic income would be, it'd be like the government directly subsidizing general purchasing power, and lot's of that will come back to the government in the form of taxes. It's like the opposite end version of corporate bailouts and tax giveaways.
Looking at a number like 7 trillion from that side, suddenly makes it way less intimidating and way more appealing. It's not like money is some finite resource that has to be mined in deep and dangerous caves; When it's about saving banks, Big Whatever or waging wars, against something or somebody, there always seems to be more than enough of it?