This requires a good eye and good deal of knowledge about the brand histories and what not.
Back before the war, Louis Vuitton was famed for its quality and customer service; the luggage series was especially made so it'd act as flotation devices in case the ship sank (imagine having a laptop case that'd act as a parachute when your plane crashes. I'd buy that). Each was serial-numbered, which the central office kept records of, and they fixed it for you, free of charge, any time. This is why LV is so famous as leather goods brand. Same with Coach. I have a Coach handbag that has serial number stamped into the leather, and I can bring it in, 10 years from now, to get it re-serviced, for free. It was a life-time investment. Hermes goes one step beyond: they have ONE leatherworker PER bag, and only that person touches your bag, period. (Freed of London, a ballet shoes maker, also does this with their shoes. ONE shoemaker PER dancer.)
Nowadays, you can get two kinds of Vuittons and Coaches; the really thin, plastic/cloth ones, and the actual leather ones that have almost no logos on them to indicate the brand. The former is marketed for the general population that wants the prestige of carrying LV around; the latter is for someone who is seeking the good ol' quality and customer care.
Same with pens. Pelikan produces really cheapie pens, and then they produce Souverains; my father can bring in his Souverain, from 1980s, to a Pelikan office and get it fixed, if it breaks. It's serial-numbered and they have the records in their office. Same with my MontBlanc (although I think my MB demands a servicing fee now... they've gone cheap). They also have tighter quality control. It really is about the customer's ability to discern quality; do you just want the Pelican beak poking out from your pocket? Or do you want skip-free, gold-nib/platinum-nib fountain pens that get service from someone trained in the Pelikan pens?
Brand-buying isn't just about having the prestige. For many of us, whose peers won't be able to tell the difference of prestige between a really low-end Waterman and a high-end Visconti, there isn't much point of purchasing prestige anyway. It's also about trust in the quality of the product. "It's MontBlanc, they won't give me a dud" is what I think when I go in to look at pens. Now, I don't know if people do get duds from higher-end brands, but I've never seen a dud from Souverain or Visconti or Conway. I don't use flex nibs so I can't say anything in this regard, but I'd think gold nibs would flex more easily, as well. It's also more resistant to corroding, so iron gall inks can be used with more comfort. And the weight of my MB is superbly balanced; I find that a lot of pens become top-heavy when you put the cap on the tail, therefore making fine control of the pen a little harder, but this doesn't happen with my LeGrand.
They really are about priorities: are you buying high end pens because you want to look sophisticated? I often find these people not having much knowledge about pens and buying them blind, online (now, collectors are a different stock. They just want variety, and quite a few have everything from Varsities to collectibles), probably because having that white star would suffice. Then there are those who seek good use out of their pens; those tend to go into a brick-and-mortar shop and write with it to see how it's balanced, how it fits into the hand, the length, the width, the quality of the nib, e.t.c. Those are just seeking the ultimate pen, the kind you'd use until the day you die, and if you're going to use it for the next 40, 50 years, what's a 1000 dollars? That's 7 cents a day.