here is one ad...
Two Full Size Marty Subwoofers, 18
www.usaudiomart.com
Even paid to have it listed front page.
I have one sub listed at $650 and the other at $850, or $1,400 for both. (Two different drivers so 2 different prices)
The boxes are nice plywood, but using the old style GSG MDF flatpack, the cost to build would be $550 for the flatpack delivered, about $575 for the B&C 18DS115-4 18" driver (currently on sale), another $100 at least for duratex, hardware, etc. That's at least $1,200 materials, more for plywood i assume, plus at least 5 hours of labor. Asking $850
The FaitalPRO driver's street price is usually a bit higher, now about $675 shipped, and I am asking even less for that one, just $650 - less than the price of the driver alone
Seems like priced to move fast.