An iPhone is also quite a technological challenge, yet Apple doesn't spend nearly as much making it as people are willing to pay. Same goes with these bags, they are a luxury item that people will pay far over the production cost for. You literally buy them to show how much money you have, so it's the brand doing most of the work, and the bag-making process just needs to be somewhat professional.
From what I gather the factories in China that make the real thing will also make extra copies of the real thing, thus making it extremely hard to tell the difference.
The social element is maybe the most interesting, it's like a hobby for these ladies. What I've noticed through my life is there's always people who do some kind of cottage buying-and-selling on the side: friends who buy luxury watches, collectible cards, used cars, restoring old laptops. There's something universal about that instinct. Being socialites it makes sense they gather about this particular thing.