A new Amex Offer for purchases at Amazon appeared on my account today. I have it on both my American Express Platinum Card and Everyday Card.
Get 2 additional Membership Rewards points per dollar spent on eligible purchases made using your enrolled Card online at amazon.com or via the US Amazon mobile app by 9/30/2019. Limit of 1,500 Membership Rewards points.
2 additional Membership Rewards points could add up to 4x MR on Amazon purchases if you use a card like the Amex Blue for Business Preferred card, which already earns 2x MR on all spend.
I often use my Chase Ink Cash to buy Amazon gift cards at Staples for 5x Ultimate Rewards points. This is a good alternative to those who don’t have Ink Cash.