Why wouldn’t it? I’ve heard many different explanations for the US’s wealth, but never that it’s wealthy because it saves on expenditures. There is also a solid case to be made that healthcare specifically would, if socialized, drive up productivity, earning power, and reduce fiscal risk (and risk aversion) for many demographics, all of which are good for GDP and other measures of a country’s wealth.
As for mass transit? It has costs and benefits too, but they’re a drop in the bucket compared to healthcare costs.