Lets consider, for a minute, the First Watt SIT-3.
What are you paying for? The Black box? The handful of components in it?
Big difference don't even know how you can compare.
A Nelson Pass (god) designed black box, still multiple x less $, with still more parts costing inside.
Not what come down to a Chinese $100 subwoofer plate amp module, built here https://www.youtube.com/watch?v=EZCxCg-QWDQ&feature=youtu.be
Cheers George