$6k, that's where I have a problem as well.
To me, the Lang is an "OK" smoker. its built well, and has a decent design. And looks like it would last a long time. Not very attractive though, definitely not a high end build. And it troubles me that owners report not being able to go more than an hour with out adding wood. That's would be a big problem for me, wondering what design flaw is causing that. This size smoker should be at least be at a 2hr maintenance cycle.and for $6k I would expect that.
Why wouldn't someone decide rather to take advantage of all the awesome information that is available on this site, and sit down and put together a set of plans for what they would feel would fit their exact needs, let all of the experts on here help fine tune the design, then hire a local welder/fabricator to build it?
Honestly, $1500.00 worth of material , and another $1500.00 of labor for a good fab shop would build you twice the smoker for half as much. And I'm talking about a nice size trailer pit.