Earlier quoted context omitted.
What numbers, specifically? You didn't cite any and there haven't been many real-world studies or experiments to produce data on the costs/results of a basic income program. Something this complicated isn't going to be accurately modeled by a couple economists purely using estimates...
Caveat: Not a professional analysis, and not the OP. There's 248 million people ages 16 and older in the US, of which 63% are in the labor force[1]. So 156 million people are available for work (not all of whom are employed). Total population is about 330 million. If each of them were to get a basic monthly stipend (this is everyone, including infants) of $1200, that's $396 billion per month in payments. Per working…
Welfare currently pays more than a minimum-wage job in 35 states, even after accounting for the Earned Income Tax Credit, and in 13 states it pays more than $15 per hour.[1]
In fact, in 33 states and the District of Columbia, welfare pays more than an $8-an-hour job. In 12 states, including California, as well as the District of Columbia, the welfare package is more generous than a $15-an-hour job. In Hawaii, Massachusetts, Connecticut, New York, New Jersey, Rhode Island, Vermont and Washington, D.C., welfare pays more than a $20-an-hour job, or more than 2.75 times the minimum wage.[2]
[1] http://www.cato.org/publications/white-paper/work-versus-wel...
[2] http://www.cato.org/publications/commentary/why-get-welfare
Of course, there are incentives to work still, but $1200/month and accompanying tax raise may kill them for many more people than now.