> What's the appeal of collecting high priced watches?

You can carry them on your person through airports and other places reasonably unmolested in a way carrying a bunch of cash isn't so easy.

> Is it kind of like art collections, where its a decent store of value

Art doesn't store value: It trades whatever number the parties exchanging it want it to have, so those parties can manipulate their total annual revenues, which might be confused with value if you cannot think of why else someone would want to tell other people they made more or less money in a year, but is not valuable to anyone else.