There are
more than 20 studies which show single payer is a net savings for Americans over the current system. Cost is a perception problem, not a real problem.
Now, we live in a country where a large percentage of the public doesn't believe in climate science, so the actual facts aren't going to matter. Sanders does need a way to answer those questions that do not make him appear to be fudging. He has a ready answer in the actual math but I can understand he is hesitant about turning this into another arena for the Republicans to blat their anti-intellectualism and the media to gleefully set it up as a tennis match.
I think that's the ultimate best way to deal with it, though. It will at least get all the Dems on board and shut down the opportunists like Carville.