More opinion incoming: few high end suppliers have really made it big. Key seems to be doing ok at the moment, and I understand that Kohs is still bringing in models for the extremely high end.
The two that died are the ones to wonder about. Henry won't tell Stephen why he stopped, but he had plenty of customers and a profit- making price that was no obstacle. And KTM USA is rumored to have produced two definitive models and stopped cold. I have a friend with an FEF, and he says it is the best model he has ever seen, operationally and otherwise.
CLW tried to move in to the high end mechanism business, and as I understand it, $750 will get you a pretty good mechanism to this day - but demand is in the onesies and twosies. A fellow forumite produces them in extremely limited quantities.
Apparently the secret to offering sort of high end models is to offer a line of profit-making low end stuff to support it. Check out Lionel - they periodically offer Hudsons to the very high end tinplate market, but support that effort with giraffe box cars and pink plastic steam models.
Henry Bultmann was widely acclaimed, especially for that last 4-10-2. He is an avid O Scaler. If he was making a decent profit for his efforts, it is difficult to believe that he stopped because somebody ripped off a couple of pilot models. And bankruptcy is highly unusual in a profit- making business.
All of the above is hearsay and opinion. I have absolutely no facts.