On that particular point which Adam raised (post 34 which I noted as helpful), I started researching exactly how many camera manufactures use Sony made sensors - and what the actual spread between different sensor makers, is.
It is a big task to collate and I admit I gave up and was distracted by the Ashes.
I think that (as one example) Manfred would be more interested in that particular area of Photography technology and history than I: I think no matter how many sensor manufacturers there are out there - the ROI argument would stand true for most of them.
WW