Welcome to the world of retail. Scuba gear isn't much different than watches, stereo equipment, or cameras. As a mater of fact, I understand one of the big online scuba dealers is owned by the same firm that has been selling cameras for decades.
"Grey market" has all the same issues in scuba as it does in the other categories, with the added complication that if your camera craps out, you can still breathe.
That said, a lot of my gear is from the more reputable mail-order sources. And a lot of it is from a LDS that knows I know the online prices, and "helps" in pricing, within their dealer constraints. I have found if you mix in a bunch of non-mainline things with your big purchases, I can get "equivalent value" to online, or close enough that I'm willing to do my business locally. Amazing how quickly things like spare mask straps, hose protectors, bags, fish books, bolt snaps, lights, etc., addd up!