I suspect it's almost impossible for a business run on high margins to compete in a low margin sector. I can't remember an example.

Apple is very successful in the laptop and smartphone markets (both are more or less commoditized and very low margin). Of course due to the openness of the platform IBM couldn't really differentiate their PCs enough to justify higher margins.

True, although Apple does ignore sectors where they can't maintain their margins. They no longer make printers for instance and despite an obvious interest they have never sold a TV.

I think what I'm saying is if you have a model where you make 30% to 50% margins then going after business that can only attain 3% to 5% margins is never going to work.

I think that Apple smartphones and laptops have higher margins than most phones and laptops. Apple has done very well at making a brand, not just generic commodities.