There are dozens of virtually identical variants of this dock on Amazon from Chinese sellers that range from $30-$40. I tried one myself and loved the design but after my watch failed to charge twice in a week I sent it back. Most of these top out at less than 30 reviews and when sorted by new, you'll find a lot of people experiencing the same watch charging issues.
Have you had better luck with the amp mobile version? I've been curious as to whether Amp's is the official version and all of the others flooding Amazon are knock-offs, and if that's the case if theirs fairs any better in the watch charging department?
As I said I really loved the design and have struggled to find a suitable replacement.