Ifonly, Well it depends on themake and specific model of watch, my oh has made 20% profit on the last few watches he bought and then subsequently sold. Diamond jewellery, no you wont make a profit,agreed.However, you wont make the loss on a rolex etc that you would on an ebel.
As for the diamonds, i have had a diamond bezel on the last few watches ive had over the last 15 yrs and theyve not been in or out of fashion. Its what appeals to you really.