Good points. None-the-less, Caveat Emptor does apply. In the case of the Quest products the certified lab testing results are available (some have been posted here). If one is looking for simple 1 or 2" fiberglass panels, it is possible they'll do better from a price perspective by shopping online vendors. In the case of Quest, the vast majority of their products are engineered products. Several factors come into play from the perspective of the manufacturer. These include individuals purchasing certain products and then noting they didn't do such and such which, in the end turns out to be, the use of the inappropriate product for the problem, incorrect placement or mounting of the product, or use of too much of the product (yes it happens).
Controlled distribution certainly doesn't make the product perform better (or worse); but, at least there is a qualified individual working with the end user to see that the end user is getting whatever it is that is best suited for their specific application. Good bad or indifferent, there are very few items in this industry which are available directly from the manufacturer. (Controlled distribution, btw, doesn't imply controlled pricing ... and here in the U.S. that has to be true.)
For the latter, comparative testing is non-existent.
Sad but true, that's why I've stated before, you really need to get the third party certified lab test results if you're buying a product for its acoustical properties. (In the case of the Quest materials posted here, the lab test results are included.)
Actually, truth be told, I believe the consumer is better off with the controlled distribution or dealer network model. If the manufacturer had to deal with the entire universe of end users calling up for questions, getting pricing, placing small orders, whatever, that manufacturer would have to have the staff available to handle it ... that overhead would be reflected in the price. By the same token you'd have one, and only one, source for a specific product. In the dealer model, that overhead cost is reflected in their offering price (granted they want a profit as well) but offsetting that is price competition due to multiple sources of supply. I don't think the dealer's profit margin affects the end pricing model that much either. Profits tend to be calculated as percentages thus as the overhead of the manufacturer goes up, the profit percentage may remain the same but the raw dollars increase. Oh, well, so much for this topic .... back to acoustics please (if I had wanted to be an economist, I would have taken two semesters of econometrics ... yuk.)