Subguns are pretty limited niche weapons at this point in history. The shift has been more toward compact carbines that use the same ammunition and magazines as the standard infantry rifles and then what used to be CQB subgun turf is getting more into the realm of slightly larger format high capacity full power variants of service pistols generally referred to as "tactical handguns".

The idea on the tactical handgun is not so much concealability but portability. Such handguns are legal in Canada and 10 shots of .45 in a modern format handgun is just fine for that. While subguns could be "effective" out to 200 meters, real world, its 50 meters and a glammed up tactical handgun can do that without the legal issues involved with the subgun. Cost issue is relative to the relevancy of the laws in obtaining the weapon more than cost of manufacture or complexity.

Regarding nuances of law, if you don't commit to what it takes to be combat effective, then you will not be combat effective.