People buy "expensive" watches for a variety of different reasons, but by far the most common amongst non-WIS people in my experience is that they have a bit of cash and want something that represents something to them in terms of image and the investment they've made. And inevitably, 9 times out of 10 this draws them to Rolex in the first instance simply because of the brand strength and recognition. Rolex has history (although admittedly not as long as some), and their watches have been worn by some iconic people over the years, but to the "layman" (and I don't use that in a derogatory sense) Rolex are simply "the best watch in the world" because they have an incredibly well managed brand image, everybody knows them, plus they are (relatively speaking) expensive.....so that makes them the best, right?
Things like 904L steel, or in-house movements mean absolutely nothing to 90% of prestige watch buyers. There are several Submariners on guy's wrists in my office, and to a man, not one of them knows anything about watches other than "it's a Rolex". From a WIS perspective it's a shame that some of these guys are missing out of some great alternatives.... but the fact is, most people honestly don't care, and I'm absolutely fine with that.
Of course, us WIS-folk buy Rolex too as they're fine watches (I've owned 2 myself and potentially looking for a 3rd), but I like to think I'm personally buying for more than just the name.
It's kind of like cars - when people have a little bit more cash than usual to spend on a car they may gravitate to something like a BMW, a Mercedes, or an Audi.....often for no other reason than they are perceived as prestige brands, without considering any other factors. But let's not forget that these brands, and of course Rolex, didn't get to the position they're in by making a poor product. No, Rolex make very nice quality watches, so if non-WIS people are drawn to them, then they are getting a decent item for the money.....and as I said above, most of them care only about the image and/or the brand name.
Another example was the Omega SMP. For years it was probably the most common prestige watch seen on wrists the western-world-over. And why was that? Goldeneye and Pierce Brosnan's James Bond. Yes of course it was also a very classic, well styled and well built watch (plus being expensive enough, but not excessively so), but it's rise to world domination was driven by the James Bond renaissance of Goldeneye, and the image it therefore portrayed. Again, as with Rolex, the SMP delivered in terms of quality of product, so the groundswell continued, but with the general public it's success came from Bond, and the fact that owning an SMP would somehow make some of Bond's charisma and style rub off on you. (And yes I've owned 3 SMP's over the years!
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Another example is a friend of mine at work was recently looking to spend around £3k on a watch, and I was suggesting various brands he could try (both pre-owned and new) - Tudor, Omega, Breitling, Panerai - but in the end he went for a massive, fully polished Oris. Not a bad watch by any stretch, but he could've done better for the money (IMO), but he said all that was important to him was wrist presence. Nothing else. And he's a very well educated guy : it's simply that watches don't interest him enough for him to look past the aesthetics.... and what he wanted was something "big and shiny by a decent recognisable brand, that will last". Not necessarily a bad reason to buy a watch at all, but to him that was absolutely all he was looking for, so it's not for me to say he's wrong to do that. It's each to their own. (It made me laugh though when I showed him a Panerai, and he just looked and said, "Nah, never heard of them"!
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At the other end of the same scale you get people who will buy almost anything (almost irrespective of the look), if it's expensive enough....and therefore perceived as making them look rich and/or successful. Why else would that truly hideous $1.8m sapphire crystal monstrosity made by Richard Mille (the RM 056) ever sell otherwise?!
If it was made of plastic (and not just LOOKING like it's made of plastic), I'm pretty sure no-one would like it.....but no, it's $1.8m so to some people it's the greatest thing ever. (And I'm just talking about aesthetics here, not the engineering which is undoubtedly top notch).
Essentially people buy watches (like they buy any item) for a variety of reasons. No particular reason is more right or more wrong than any other. It's like anything in life - the more you get into a topic, the more your eyes are opened to other options, but that's entirely up to the individual. If you aren't THAT interested in a subject, but still want to be part of it, you will only ever follow the crowd for fear of making a (potentially expensive) mistake due to a lack of knowledge.