But should we believe him? How do we know he's a reliable source?The source is exactly the same guy ("Bits n Chips") who tweeted that Threadripper @ 16 cores would cost $849. At the same time he tweeted that the manufacturing costs for that chip are $110-120! Therefore, since the chip is little more than 2x the pins and 2x the cores, wired together, It stands to reason that a single 8-core CPU would cost about $60 to manufacture.
As for the "2x" idea - it's, sadly, not that simple. Production cost includes packaging, some allocated cost etc. This would make a difference.
Keep in mind Ryzen CPUs are often bundled with a cooler.