Looks to me like just a pontoon boat on-plane (on-step). Not even a true hydrofoil.
Can't say I would ever pony-up $400k to own one.
Especially when you can have a real Tupolev N007 for half that amount. Seats 6, carries 400kg payload, and travels at 125kmh - powered by a 9 cylinder radial.
Or maybe you could pick up a used Russian
Ekranoplan:
