It would be interesting to hear Aqualung's position on it's marketing strategy. Some here have suggested Aqualung should sell direct or lower their price, etc....
I'll take a guess at one possible reason for the way things are the way they are...
Can the average Joe buy their car direct from Ford, Nissan, Chevrolet, etc on thier websites??? Don't think so. The same is true with many many products, so Aqualung's and ScubaPro's stances are not all that unusual when looking at the overall merchandising and marketing picture. Part of what's happening is that our product system has evolved over time to where the manufacturer is generally not directly involved with the end user in most cases. This may change over time, but at this point it's not that common.
Aqualung, ScubaPro and others who follow similar policies choose to continue following the traditional marketing methods... produce a product, establish a wholesale/rep group who in turn services individual dealers who in turn service the end user of the product. Over the years/decades/centuries this system has been proven to be fairly efficient and "can" (not necessirly "will") manage sales and followup service of a given product more efficiently that trying to go from manufacturer and end user without the middleman.
Now some other stuff... let's look at grey market and "service". With a grey market product, if the manufacturer has no official relationship with the marketer then they have little to no control of what happens to their product. Going through their normal dealership channels, Aqualung and the others who follow thier system have control in the sense that they know their dealers are supposedly knowledgeable in the field of diving, can service the equipment, and more importantly are selling the product to an end user who is supposed to be trained in diving...
One of the biggest concerns for the manufacturer of scuba equipment is liability. Rick mentioned earlier that this is not like buying a copy of a DVD, it's a product that was originally made by the manufacturer.. however, if someone hands me a DVD, or a copy of an original DVD, and says stick it in that machine and you'll get a movie to view... it very probably won't kill me when I try it. If someone hands a BC, tank and reg to a neophyte and says "there's the ocean, put it on and get in there and you'll be diving" it could lead to lethal problems in quick order. People tend to forget that scuba gear is a product that is basically life support in an foreign non-"human friendly" environment that requires a different level of care/management/training/whatever than most consumer products. Just in the last couple of years there was a case in Oahu where a person died on a dive, I think it was bolting to the surface, it went to court and cost the dive operator a bunch of money, it cost the original manufacturer of the equipment that diver was wearing (even though they didn't prove there was anything wrong with the equipment as manufactured) even more... they're on the hook no matter how stupid, careless or just plain unlucky the end user is. The system they use at least spreads the liability around a bit, as well as helps relieve the liability because if their dealers are following thier dealership agreements the odds are that the end user will be using appropriately serviced product as well as appropriately trained in it's use - now that's not always the case, but at least on paper it should be.
Basically, there's a lot more to what meets the eye than just price.