1100 USD for custom Ti? That's crazy cheap!
Even if it does go up a bit with the design changes, that's well under what I was thinking.
I think Wkkie waiting to see if they can do anything outside make hardtails or their own flex-stay dual-suspension design will be key here. The people at Waltly are manufacturers, not designers in the true sense. You're communicating your idea/design via e-mail with someone in China, who's communicating with someone doing the tech drawing, who'll then passes the drawing to their production team. Even with a hardtail like what I'm getting it would've been easy to end up with the wrong thing, but trying to explain a dual-suspension design and get an accurate tech drawing back that their production team can actually build is fraught with peril. Also, compared to a hardtail it's a very different thing to build a dual suspension bike, as they require totally custom jigs and are essentially two separate frames that have to bolt together and align properly (and maintain all the necessary crank and chainring and tyre clearances at all point of travel). I also doubt they're doing or able to do any stress modelling, and responsibilty and choice regarding tubing and design ultimately falls on yourself. Getting a DH bike made up that works as intended (even just a modded copy of an existing bike) that will deal with the forces you can put into it would be seriously time consuming and risky, as you have to know exactly what to ask for (down to precise dimensions and location of pivot or linkage attachment points and then hope they can translate it at the other end.
I had only minor hiccups with designing my hardtail frame and found them easy to deal with, but what I'm asking for is what is typical for them. They'd need to change some of the mounts attached to the jig and custom bend a couple of bits of tube but that's it. You're effectively dealing with a manufacturing facility, that just happens to have some basic understanding of rigid and hardtail bike design. They're not hardcore bike fanatics that live and breathe linkage designs and cutting-edge geo.
Even if they will build Wkkie a single-pivot frame for that price (and hopefully they will since that's what they quoted him on), I wouldn't hold my breath that price would hold for any similar future orders once they figure out the extra material and labour involved.