What AMD is doing is really insane in my opinion. I'm not sure if they are pricing their processors low on purpose and/or if they have found a way to manufacture cheaper and/or Intel was screwing consumers with their pricing since they were so dominate.
No matter what, AMD is able to provide something that is measurably better and significantly cheaper than the incumbent, and if the blue ocean strategy holds, they should become the new incumbent in the near future.
AMD spent less money on TSMC's research. Apple has been bankrolling TSMC to get the latest and greatest process tech.
AMD reached 7nm not because AMD put the R&D research into it... but because they can ride on the coattails of Apple and TSMC's investments.
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TSMC and Apple simultaneously benefit: TSMC can spread the risk of the 7nm process to more companies. Apple still gets first-dibs on the technology (but they only need ~6months worth of factory time to build all the chips they need).
Its more surprising that Intel managed to stay ahead of TSMC / Apple for so long. The economics are kind of against Intel here. The more people working together on process tech, the more efficient the results get.