That's an ongoing problem...when you're dealing with little boutique manufacturers, you're not dealing with a company that can farm out its PCB fab and stuffing to someplace in Shenzhen. Sure, big firms can do that easily enough, but when the "manufacturer" consists of one or two people, supply and demand kick in with a vengeance.

As for stats, well, Sweetwater has a whole website and print catalog section dedicated to Eurorack. If there wasn't a sizable market for that, they wouldn't have bothered.