Supply problems more likely
Another more likely explanation for the difference in sales are lack of availability. The first version was introduced in March of 2015 but wasn't widely available until September of 2015. Version 2 was introduced in September 2016 but was not even available in the Apple Store in Berlin for the first month or so. It might be now haven't checked the last 3 weeks but it is pretty hard do sell something you do not have and I would pay the extra 100USD for a waterproof version with build in GPS. The first quarter without delivery constraints will tell us more about the success of the watch, not a quarter where they are having problems producing enough watches