We can also do things like spend less on bombs ($500B less IMO), end all corporate subsidies (either tax reduction or cost shifting like agriculture subsidies) . Additionally we will save a fortune from how we presently treat poverty symptomatically. Someone in jail costs upto $168K a year, homeless people cost a fortune to the healthcare system[1]
The list goes on and on. Its cheaper to do BI than it is to do what we're already doing. It doesnt cost $3T _more_ it costs less than what we _already_ spend.
Everyone I've heard seriously propose a basic income has coupled it with a progressive increase in federal income tax, so that individuals earning above $50k or so would receive no increase in their BI+earned income-federal income tax.
So the actual ratio of basic income provision to federal income tax would be much lower than 1:1. 1:2 seems more reasonable.
Then, the expectation is we would significantly reduce spending on distortionary and expensive bureaucracy like food stamps, welfare, minimum wage, school lunches, and housing subsidies.
I imagine overall people in high income brackets would pay higher income taxes to the extent that we wanted to balance the budget.