The high-end apple watch (SS, ceramic, titanium) have a very bad resale value compared to aluminum because it's hard to sell a used S4 more than a brand new S5 even if it's stainless or titanium.
So when the S6 will be on the market, you will never be able to sell your S5 SS more than the entry level S6.
People prefer to have the last one with more feautures than the old "luxury" one.
You just have to be aware that high end AW are just for pleasure and cost a lot.
It's just a "luxury" choice
If only it was that simple. Sometime people purchase the SS or Ti because of allergy or because there particular disability makes one need the sapphire crystal. One should not assume that one is just making a luxury choice.