That is cool. Havent seen one in a very long time.
Cool but $5000??? Wow, you'd have to really want one to pay that.
It's a fairly simple gun to make. No doubt you could find a gunsmith to make you one for far less.
Crazy prices no longer surprise me, check out these silly sales for Serbus...
https://www.gunbroker.com/item/926047416
https://www.gunbroker.com/item/928103988
Think about how many suppressor baffles you could fit in that thing.