Originally Posted by john1928

Delta has the numbers and knows how the math works. While the annual fee generates some revenue for them and is part of the story, every dollar spent (and thus mile purchased by Amex) generates incremental revenue at or near 100% profit margin since it costs them zero in fuel, utilities, flight crew, plane payments, etc. I suspect (gut feel, no data), particularly with the changes between the card tiers, that the Reserve card holders probably average the highest annual spend of the various tiers. If those customers perceive the value of that card as being lower perhaps some of them drop to a lower tier, or drop a delta card entirely and move that spend to a generic Amex or other co-branded card.