That price is a meaningless comparison, you can't buy the Apple processor in retail. What's the cost to procedure the AMD part? Something similar I'd guess.
Two and a half times higher cost to build a slower, more power hungry CPU is not actually very similar.
You can argue that this particular Ryzen has a higher gross margin, say 50%, and lower ASP than $300, but that only gets your cost down to what, $140? And with RAM costing extra.