During the Feb. 7 Democratic presidential debate, former Vice President Joe Biden once again questioned the price tag of “Medicare for All,” the single-payer health care proposal championed by one of his key rivals, Sen. Bernie Sanders of Vermont.Biden argued that the plan was fiscally irresponsible and would require raising middle-class taxes. Specifically, he claimed, the plan “would cost more than the entire federal budget that we spend now.”Medicare for All’s price — and whether it’s worth it — is a subject of fierce discussion among Democratic presidential candidates. But we had never hea...