The GPS model is currently listed at $330; that's $100 less than its original price. The more expensive GPS + cellular Watch is on sale for $370, meaning you'll save $160 off the original list price of $530. We've never seen Series 4 prices this low.
Apple has moved on to the Watch Series 5, but the Series 4 is still a great watch. The new Series 5 features are pretty subtle, and they're things most people will be able to live without -- like an always-on display and a Compass app. The Series 5 basic, no-cellular, GPS-only aluminum version starts at $399, and if you add cellular, that will bump the price to $499. So, if you're looking for a solid watch but don't want to pay full-price for a Series 5, these Amazon deals might be the way to go.
Buy Apple Watch Series 4 GPS - $330
Buy Apple Watch Series 4 Cellular - $370