How much would I spend given unlimited funds? Probably not as much as some might imagine. I would want a beautiful looking, beautifully made and finished watch with a superb movement that did the job really well in terms of precision and accuracy.
I am not interested in:
Precious metals and jewels. I don't mind yellow gold, but I'm much happier with steel these days.
Too many complications. Keep it simple. Perhaps a date, or a chronograph or GMT for the right watch. I don't want one of these things that has 25 complications of which I wouldn't use 20 and wouldn't understand 10.
"Ars Gratia Artis". Some of the really high-end watches are an amazing tour-de-force ("because we CAN"), but a lot of them look hideous and often it takes some time to work our how to actually tell what time it is.
I'll spend under £20k and have one of these.
Or I'll spend less than £10k on one of these: