st and nxp and atmel make cortex-m4 and cortex-m7 microcontroller
price >6$
and at this price i can buy cortex-a8 1ghz + sdram chips
why they manufacturing cortex-m4 and cortex-m7 at this price and i can buy high performance cortex-a8 1ghz cpu at this price ????
I think this question is a bit out of the scope of this forum. Maybe the A8 is cheaper because of
the volume (it's used in many tablets and phones and sells by millions).
Most likely is related to what doraemon explained: very high volume production.
One of the key factors in reducing silicon cost is the wafer size. With high volume one can run larger wafers.
A large volume also means larger continuous runs. This means less setup changes, better optimization of parameters, etc.
I think you answered this on the initial question by yourself. The high performance microcontrollers used in mobile phones as the Cortex A8 variants are an example of this
Have you actually looked at the ARM website, they have a pretty good explanation of the space that each family is targeted towards.
A - Application (basically things that are running an OS and interact with a human)
R - Realtime (basically stuff that runs fast and responds autonomously to inputs, like robotics, self driving cars etc)
M - Microcontroller (embedded design, SDR, etc)
specifically the M4 & M7 have DSP and floating point cores embedded. So I imagine besides the optimization for power and performance along with the extra baggage of extra features the die could be larger and the yields are therefore worse than the A series. I'd imagine the R series is probably even more expensive as the market for such things is somewhat limited at the moment.