Slight error near the end
Another way to put this is that consumers benefit by 50 cents from every dollar they spend at Walmart. Without Walmart, prices would be twice what they are. And what's the benefit that the Walton family get from this? Well, on a 3 per cent profit margin and they own 50 per cent of the company then it looks to me like they get 1.5 cents out of every dollar. And consumers getting 50 cents on the dollar, the entrepreneurs getting 1.5 cents looks pretty close to our Schumpeterian result of the entrepreneurs getting 3 per cent or less of the total value created.
Surely the Waltons enjoy 51.5¢ of savings for every hypothetical-pre-walmart-dollar (HPWD) they spend? They too benefit from the downward pressure on prices, plus they still get their half of the 3% profit margin.
I'd like to see the supposed benefits of Walmart to the US economy graphed against a hypothetical one that existed without Walmart's influence. For example, without Walmart the resources it now uses would have beeen spread out over a wider group of companies and individuals rather than being concentrated in Walmart and the Walton family. Spreading those dollars out amongst more people's pockets (eg: that is, whatever businesses that would have sold the things and stuff had Walmart not existed) would have meant more people would have had more to spend. And by your own assertion they would have been spending twice the money which would generate 2x more tax revenue for the State and local communities leading to better public services (roads, schools, etc.) Higher prices can also support higher wages which could have created more jobs in the US manufacturing sector in a virtuous cycle, with wages linked more closely to productivity.
There's probably some bit of economics knowledge that refutes everything I just wrote; I am keen to hear it if so.