I don’t think so, as Fairphone once calculated the core-module at 314.00 Euro as you yourself proved here:
And the materials alone - in that old calculation - amounted for 230.30 Euro. Adding manufacturing and assembly (37.20 Euro), shipping and handling (???) to it, you end up with at least 270.00 Euro, based on that outdated calculation.
Should that be true (I would expect slightly higher costs by now) vireo makes about 70 Euro on it, which equals 26%; about half as much, as you guessed.
On the other part I agree.
I don’t remember who posted first, that the core module is for sale on vireo, but it surprised me a lot, as Fairphone does not sell it. If it ever was sold: see the thread of the posting I linked to.