Earlier quoted context omitted.
There are plenty of cheap NVMe SSDs that can push 3.5Gbytes/sec (Samsung 970, Adata XPG). Even with dual 10Gbe NICs, you can't match that, nor the low access times of local storage. But I do agree that SAN storage is the norm here.
Thunderbolt 3 can beat that though
Mind you, you'll pay $15K for it, but if you're in that business you can well afford it even if you're not a top tier Hollywood production shop.
Given that your storage array costs that much, the fully loaded Mac Pro price (somewhere in the $20K range?) is not that outrageous. The people who use Red cameras and G-Tech storage arrays are the Mac Pro demographic Apple is going for here.
Disclaimer: I used to work with G-Tech but no longer there.