Bob Samuels of the AFT has calculated the cost to society of free public higher education. His magic number is a cost of $127 billion annually, a figure offset by a variety of savings. (For instance, we’d see a significant reduction in the cost of student loan programs. And we could reap more taxes by ending tax breaks on on education-related investments, which turn out to be a handy tax shelter for the rich.)
By my calculations Samuels’ total cost, never mind the offsets, would be approximately the same amount of taxpayer money as the cost of war since 2001.
I haven’t got a clue how to calculate the total social benefit of free college tuition at all public institutions of higher learning in the U.S., but I am pretty sure we’d get more out of it than we get out of the war in Afghanistan.