Considering they mark most things up by ~22% this almost negates the premium they charge.

Details
Get a one-time $15 statement credit by using your enrolled Card to make a single purchase of $75 or more online at instacart.com by 2/16/2016.

Terms
Valid online only. See merchant website for delivery availability in your market. If you order an item during the offer period but the delivery date is after 2/16/2016, it may not count towards determining whether the purchase qualifies for the offer. Enrollment limited. Offer is non-transferable. Must add offer to Card and use same Card to redeem. Only US-issued American Express Cards are eligible for this offer. Limit 1 statement credit per American Express online account. Statement credit will appear on your billing statement within 90 days after 2/16/2016, provided that American Express receives information from the merchant about your qualifying purchase. Note that American Express may not receive information about your qualifying purchase from merchant until all items from your qualifying purchase have been provided/shipped by merchant. Statement credit may be reversed if qualifying purchase is returned/cancelled. If American Express does not receive information that identifies your transaction as qualifying for the offer, you will not receive the statement credit. For example, your transaction will not qualify if it is not made directly with the merchant. In addition, in most cases, you will not receive the statement credit if your transaction is made with an electronic wallet or through a third party or if the merchant uses a mobile or wireless card reader to process it. By adding an offer to a Card, you agree that American Express may send you communications about the offer. POID: BXSI:0001