Large single crystal diamond, what is required for a nice transparent screen, is still quite expensive. This article is about polycrystalline diamond, which is not really that transparent, but is nearly as good at thermal conduction as monocrystalline diamond.
I have a Garmin with a sapphire screen. I've worn it every day for over 5 years, working on cars, in the garden, snorkelling on coral reefs.
In short, I my watch has NOT had an easy life. I've made no attempt to protect it or taken it off for anything except charging. There is barely a mark on the screen. A sapphire screen will be a hard requirement for my next watch.
I wear mine while rock climbing. The watch has been put through a lot of beating against all kinds of rock. I've already chewed through 3 straps on this watch. The titanium case is lightly scratched, but the screen is absolutely pristine!
This is my second sapphire Garmin, and it's absolutely worth the premium.
