It would be interesting to know how much it would cost in the DIY world to equal that level of performance - and how much you would have left over.
It would be far less then you think....
By rough calculations, we figured out that one of my XLERATORS would have roughly
at least 2-3 times the output of that unit in surface area and excursion. you don't have to build boxes as nice as mine, so you can go much cheaper - with a couple of sheets of Baltic Birch ply or even MDF. I really took a long look at that product and its design before my build.
Price is subject to what you invest in the enclosure, amps, drivers but one could do the rough math to figure that out..
Pair of 18" LMS's - wood to build a dual opposed box, and either 1 very large expensive amp or a pair of medium sized amps - even an ep2500 or ep4000 per driver would suffice, unless you wanted that last 3db out of each driver, then 4000w per driver.
There is no question that the Sub 2 is a very detailed build, a nice small and powerful little package, with built in amp and EQ - but certainly expensive..