Earlier quoted context omitted.
Warning: back of the envelope calculations ahead You're forgetting the fact that a basic income would obviate all means-based welfare programs, unemployment insurance, social security, etc; this means 2.3 TRILLION dollars (1.03T from means-based welfare programs and 1.3T from SS) in savings. Also, it would be enormously strange if we gave a full basic income to every infant, toddler, child and teen in the United Stat…
Social Security pays the retired 10s of Ks per year so they can live comfortably after paying into the system for their entire career. You think we should get rid of that in favor of a basic income of ~10k for everyone? That's going to suck pretty bad for the retired. You're certainly entitled to your opinion if you do think that but the vast vast vast majority of Americans are going to disagree with you.
http://www.ssa.gov/policy/docs/quickfacts/stat_snapshot/
Even if social security was completely removed for a basic income of 10k (I'll clarify again that I'm not endorsing that figure as a blanket basic income), it would be a cut of a couple thousand a year, not a cut of more than 10k as you claim. Hell you could even keep all the net SS+basic income payouts the same and social security costs would drop to 1/5th of what they are now, saving over a trillion dollars.
Also, That was like, one third of one fourth of my post. The fact that your estimate was way way off (far from "simple math") is barely changed by excluding social security.