Current 75S is 44 seats (
http://www.seatguru.com/airlines/Delta_Airlines/Delta_Airlines_Boeing_757-200_75S.php). The 75X, for example, has 26 EC seats. I find it odd DL is adding so many more. This must mean on the longer routes the 757 is being deployed there is a great willingness to pay for the seats. I find this surprising considering on many of my DL flights the EC seats are often empty once the Medallion upgrade window opens and then EC seats are later given to standby/non-revs/people without assigned seats on day of departure. Obviously DL has hard numbers and knows but the sense I get is very few people actually pay for the seats, its more a consolation prize for Medallions who don't get upgraded.