Whilst various experienced people have said, quite rightly, that you don't need an expensive "pilot" watch for flying - equally most of us have the right to own, if we can afford it, "nice" stuff. Depending upon taste, that runs to cars, clothes, computers, aeroplanes.... .... and watches. I'll bet that just about everybody reading this has items which they spent more money on it because they like it, going well beyond the purely functional.
So, there is absolutely no reason why somebody who likes wearing a posh watch shouldn't spend a few hundred, or even a few thousand, on that watch.
If that person happens to be a pilot, then it makes sense for them to have a watch that they can use for flying as well - why on earth should you take the £500 watch off that you like wearing with a suit at work, to put on a £20 Casio to go flying?
Speaking for myself, I like my old RAF issue Seiko Military, which would probably cost around £150 to replace, and if it dies I'll probably spend that. I'm wearing it now in the office, and I almost invariably use it for flying. If for somebody else that's a £5k Breitling (or a middle-eastern copy of a £5k Breitling!), why the heck not?
G