Much like timeshares, Direct Buy is appropriate for a limited audience. We were members for 3 years when we lived in Maryland, and saved quite a bit - and yes, I was quite good at comparison shopping, and compared not only local stores but anything I could get over the internet or through other sources.
But, we were remodeling our kitchen (gutted it, saved around $6000 purchasing almost everything through Direct Buy, and using local affiliated contractors), 2 bathrooms (did ourselves, but saved a bit), 2 bedrooms (completely outfitted these 2 rooms, as our first child was born 1 year after we joined), and bought a variety of other items. After 3 years, we decided it was no longer of particular benefit to us, and ended our membership. But we did save far more than the membership cost us, and ended up with better quality than we might have been willing to pay for otherwise.
We can say the same thing for timeshare - it works for us, but we know many people who wouldn't do well with it. These are people who would really benefit financially, even with a developer purchase, but would never take the time to understand what they own - the type who end up paying top $ for their airline tickets and hotel rooms because they decide where they want to go fairly late in the game. The same ones who think I can't possible be getting the same product if I buy it at a discount.
I would say the same thing to someone looking at Direct Buy as I do to the uninitiated who attend timeshare presentations - take a deep breath and decide if this is really for you. The salesman does a wonderful job of showing you how it "could" be for you, but if you're having second thoughts, don't join.
Don't fall for imagines saving - it's only true savings if you were planning on spending the money in the first place.