Annuities as UBI conceptual model

Today, I was playing with an immediate annuity calculator. For about $106K (USA Dollar), one can get a 10 year Immediate annuity that pays about $1K per month.

For $1 million, 9 people could be covered for 10 years. For $1 billion, 9,400.

Every American could be covered for the next 10 years for ~$35 trillion. Rolled out over 10 years, it could be $3.5 trillion per year.

I am better able to reason about annuities, than government spending, so this started to put the costs in perspective for me. The costs also stop being as "squishy".

UBI would be life changing for many. Those with lots of income already would be paying about 30% back to the IRS.

There are lots of optimizations. For 60% more, the term could be doubled to 20 years, cutting the annual rollout cost by 20%. I bet costs could be improved when purchasing $1 trillion of anything. Annuity rates are also not great right now, so there a likely better structures.

Thoughts?