We should not make it more than $1000 per month. Very few would choose to be poor. It would put a lot of pressure on companies to pay decent wages, though.
It also becomes clearly tenable with households of more than 1. Supporting a family of 2-3 on $24k-36k is like, yep, I've met married international grad students. Of course they'll spring for supplemental income where available, but as a baseline it is tenuously "enough".