In fact I think Standard Oil wasn't far above that by the time action was taken. They were also cutting prices and modernizing heavily. To get much beyond that

In fact I think Standard Oil wasn't far above that by the time action was taken. They were also cutting prices and modernizing heavily. To get much beyond that I think you need some special advantage like govt protection. I suspect the patent system, which literally guarantees monopolies to companies in return for a fixed fee, creates a big advantage for the leaders in tech markets. Hence modern leaders last a lot longer with more market share (and way higher margins) than they should.