I suspect some people will buy both.
No investment is guaranteed to go up forever. Though I like the odds of luxury goods increasing in value. (Side note, there is clearly, to me at least, an interesting inflation effect happening that is impacting the rich. Everything that the very rich want to buy (i.e., Art, Housing, Luxury Goods (your watches and bracelets)) seems to be increasing in price at vastly faster rates than the reported 2% inflation. Something is going on here and I don't think folks have clued in on it. But it is very nice for the rich if they can regularly buy expensive things and find that they appreciate in value dramatically during only short periods of ownership. On the other hand, buying something truly exclusive is getting harder and harder.) Agreed these watches as an electronic items probably won't appreciate in value in the way of an automatic watch that will not fall apart might. But I think that is the fact that stops Apple from charging $20,000 for the edition and "just" brings it down to $5,000 range.
As you are well aware, there are many folks out there that make $5 million or more per year. So when they get their bi-weekly $200,000 paycheck, they've got money to spend. I think Apple drops the ball if they don't grab a huge chunk of money from their most exclusive product. And even if this product doesn't sell in high numbers it sets the floor and it will make the next generation $5,000 watch not seem as shocking.
Luxury houses will only charge what the market will bear. They may have their eye on the super wealthy but they also keep their items just in reach of the upper middle class. In my opinion, two types of people buy these items, the super wealthy and those who make good money but have to do a little saving to afford them. If Apple wants to make a name for themselves in the luxury market they would be wise to copy Cartier, Van Cleef and Arpels, Rolex, JLC, etc. and price their items to appeal to both types of people. The super wealthy, as you pointed out, will probably buy the watch no matter what it costs. But Apple needs to make it attainable to not just the top .0005% but the top 2% (upper middle class making 300K yearly), if they want it to be as successful as the Cartier Love bracelet, for example.
At any rate, it will be interesting to see how highly Apple values itself, in relation to real luxury brands, in the pricing of this product.