> You can see this play out pretty straightforwardly if you assume a dollar in savings represents about a dollar of value created that wasn't then consumed.

I think this assumption is false to the point it invalidates the results. Because savings is marginal, if the relationship between value and dollars is off by only a little, the delta between net value and savings becomes huge. A good hint this assumption is wrong is if it were true, the value produced by a slave would be zero.