How much should you spend on a watch?

There are two questions that, as a watch critic, I hate being asked. The first comes with alarming frequency, and is this:
'What's your favourite watch?' Often,
before my hand can hit my face, it's
caveated by, 'I'm sure you get that
question all the time…' Or, 'you probably don't have one, but…' And worst of all, 'perhaps you can't say…', as if to suggest I'm somehow beholden to a brand, but bound to a false creed of professional
journalistic impartiality, and might - just for them - let my guard down.
The second is almost as irritating: 'How much do you think I should spend on a watch?' This is usually motivated by a form of hyper-inverted snobbery, and a trap, albeit not a very good one. 
Other times, the question is genuine,
which is just as stupid, but for different reasons. It assumes I know how much money you have, and that I know how much of that money you'd like to spend on a watch. Which patently I don't. 
All the same, you still want it answering. And there are, I suppose, some guidelines I can give you.
For example,
buy something you like. It sounds obvious, I know, but there's nothing sadder than hearing some daft lunk lament an impulse buy they later come to regret - a herpes watch. Scrutinise your purchase aesthetically. If you like the case shape, but the date window irks
you, don't buy it.
Secondly, buy something you can afford. I know that makes me sound like a man who irons creases into the front of his trousers, but seriously, don't get lumbered with a ball-and-chain watch. Remember that most watches are not an investment and are worth considerably less than you paid for them the moment you pay for them, and that you still can
buy excellent mechanicals for a few
hundred quid.