Is there some useful or convenient formula to approximate the value of Amex point in terms of redeeming them towards merchandise or Amex gift certificates? In other words,how much are 1,000 points worth? Fifty dollars in redemption? One hundred dollars towards a purchase, etc.
My experience with them was it depended on the partner.
For instance, Regent's Cruise might be 100 pts for every $1, whereas, Marriott might be 50 pts for every $1.
Look at their catalog of rewards. You'll see it clearer there.
For giftcards, you can generally get $0.01 for 1 MR point. So, 10,000 MR points gets you $100. Cash card redemptions get you about half that and are not a good value for your points. Your best value is generally to transfer your points to a frequent flier program especially when they are offering a transfer bonus. There was a recent 40% bonus for transfers to BA. There's a current transfer bonus with Delta where you can also earn MQMs toward elite status.