This thread was created without my knowledge or intentional stimulus, BUT IT HAS MY INTEREST.
I have a certain friend, @
d_c , who I could probably commission to build me a gjallarhorn --- when the time comes, though I'd consider one built by you as well if you were wanting some project fodder.
Yes - the gjallarhorn and the orbit shifter are the two most impressive subs I've heard. I'd likely strongly consider taking a pair of either over my eight sealed 18" Ultimax 18's.
BTW, @
rhyvun , you heard the T48 horn sub IIRC, from the 2013 speaker meet in the park. The Gjallarhorn is order of magnitudes more powerful!
As to your original question....
I bet some enthusiasts wouldn't mind paying $3k for something like a gjallarhorn if they had no other options in their pocket to make it themselves. Think about it --- the top tier of internet direct subs is hovers around $3k, and they do not best the gjallarhorn in the lower frequencies down to about 15hz in most any case I'm aware of. The Orbit Shifter probably has more SPL capability up top than the gjallarhorn ---- so that's a trade off. The OS is about $3.3k. (before shipping) --- but it includes a 4000 watt amp. So you aren't going to be pricing anything much higher than that and having it sell like a hotcake - since there is competition.