Does this ridiculous number of antennas even do anything or is it just marketing wank?

Phased arrays are not a joke. You can get ridiculous dynamic range with those

Unless you need 6ft of cable or you just run wires on the floor it’s more like $200 of plenium rated cable, and keystone jacks and the labor involved with the run.

My house with a half finished basement (easy access) took probably 16-20 hours running to 5 rooms.