The combination of solid gold and the obsolescence period of wearable electronics is uncharted territory.
Luxury mechanical watches need service too, it's a very standard thing in the industry. Apple can offer a CPU/screen/sensor improvement every two years for about a thousand dollars for the luxury models and owners would pay it as they pay the water seal replacement for their Omegas and Rolexes... only Apple's margins are going to be sky high because it may be an easy thing done by a grunt in a tech service shop, and luxury brands have to send your watch to highly skilled engineers sometimes in another country.
EDIT: I posted before finishing the article, Gruber thinks Apple may upgrade the electronics too, but for "hundreds" of dollars.
Of course, if you could do that though, then you're not really in the smartwatch business, since it would mean anyone could make compatible wrist-bands.
Conversely - that might not be a bad business to be in.
and also, isn't it a little bit impractical in reality as well? gold being a soft metal will wear out if you wear it? then there could be less gold than what it says on the cert?
Given the cost of parts and assuming the chunk of gold accounts for more than 90% of the price, some sort of trade in system should cover this problem.
Apple abandons devices from OS upgrades and compatibility, batteries lose their charge. It'll very quickly (in terms of "collectibles") become a gold bar with a black rectangle in the middle.