This assumes that you'd give BI to every citizen. One twist I haven't seen so far in any BI discussion is this: what if you only give BI to those who ask for it (but still with no strings attached)? I wonder how many people would bother. For example, why would Bill Gates or Mark Zuckerberg put in the effort, however small?
In general, I would expect rich people to sign up for it. Two reasons: First, they didn't get to be rich by passing up opportunities. Second, they hire people who work full-time to maximize their money, and those people will sign them up for this.
Sure, but the marginal benefit is almost inexistent. When you have billions (or tens/hundreds of millions), an extra $12k is practically nothing.
This makes me think of mail-in rebates for electronics, at a different scale. It's also weird to me to see an engineer making over $100k/yr to buy a hard-drive or GPU with a mail-in rebate, then put in the effort to send in the coupon to get that extra $10 back (I've done it myself, but I don't earn that much). To someone making >$6-8k/month, $10 is peanuts. That's also how I see this $12k for billionaires.
so the top 10 percent or so that cant be troubled to pick up 12k laying on the ground would reduce it to 2.3 trillion? How about something worthwile and make the tax rate on income over 2 million (out of the air) to 90 percent like it was post WWII and use that to help pay for it.