The HP Journal article mentions the 9% yield as if they are perfectly fine with it. They were building these chips internally for high-margin gear (as you said)

The HP Journal article mentions the 9% yield as if they are perfectly fine with it. They were building these chips internally for high-margin gear (as you said), so it probably didn't matter if the chip cost $10 or $100, as long as it has the performance that they need. It's a completely different market from microprocessors such as the 6502 or the 8086, where customers are looking closely at the cost of the chip.