The additional $75 is possibly Amex’s commission, which falls under the “fee” portion of “taxes and fees.” If you read the text box that you can access by clicking for more info it states Amex often adds in a commission.

I happened upon this yesterday. At first I called AmexTravel to inquire about the fees and taxes since the hotel did not show these if I booked directly. The agent steered me to the fine print and told me it was commission and for my “security”. I ended up getting it waived /credited back. It’s deceitful in my mind of Amex to hype a low-price guarantee on the room, the $200 credit and then essentially eliminate or reduce those benefits by lumping a commission under “taxes and fees.”