The Razer core is $499 for the enclosure only, which make the price even harder to swallow.

Considering the size of gaming graphics cards, having a NUC is kinda pointless then :)

Yes. Thunderbolt 3 supports 40Gbps and should allow for an external GTX 1070 or 1080. The cheapest Thunderbolt 2 PCIe chassis on Amazon is around $200, and I don't see why we can't have a Thunderbolt 3 PCIe chassis at this price point.