It is $0.0006 per point excise tax. Far below the difference in 5x points/miles on the Amex Platinum compared to the 3x miles on the Delta cards (Not to mention the Delta gold card at 2x). It is $60 to turn 100,000 Amex points into Delta miles. The $60 can be paid with 6000 Amex points so I guess the way to look at it is 100,000 Amex points can be converted to 94,000 Delta Miles for no cost.