The Apple Watch Series 3 is currently available at discounted rates in the US. Specifically, Best Buy is shaving off $50 from Watch 3 (GPS) price to bring the tag down to $279.
The price cut is available on both 38mm and 42mm variants. Even the Nike+ models of the smartwatch are also $50 off. A similar, Watch Series 3 deal is being offered by Macy's as well.
And finally, the Nike Store is also offering a 20% discount on the watch (LTE enabled Nike+ models specifically) - you'll need to use 20SUMMER code at checkout.