They aren't going to sell these chips anywhere close to 50$, high end mobile phone SoC's cost 60-100$ these days, even the Chinese SoC's are not that cheap MediaTek's Helio X25/X20 are "cheap" because they aren't Snapdragon 823 Exynos 8893 100$ price parts, but they are around 30-50$ also (and could be even more, since a bargain bin MT6582 MediaTek ARMv7 SoC costs 8-10$).

This isn't going to be fabbed in China, almost none of the chinese SoC's are fabbed locally the foundries are not built for that the process is too old and overall they are not intended to produce such complex silicon, there is much more to a process than just the lithography and even that is not straightforward because you actually need to do tricks to get to sub 28nm today as you often end up using higher wavelength light since extreme UV and other similar technologies aren't there yet.

The 64-core SoC's are going to be multi-100$ parts, probably closer to the 1000$ mark regardless if they are chinese or not, Cavium SoC's are about as expensive or even more expensive than some of the Intel parts they are competing against.

If China introduces a 64 core ARMv8 SoC at 50$ Intel won't be worried, it would panic to the point of them using the backdoor everyone on HN think they have via AMT rigging the election so Trump can win and then convincing him to nuke China might actually happen.

That said a 50$ 64 core ARMv8 SoC is pretty much impossible to make even in China, by China, for China.