This is not a question, but more of providing information about Delta's economy comfort seat. I email Delta to enquire about how much it cost to upgrade to a economy comfort seat, and this is what they said
Thank you for your email to Delta Air Lines regarding to upgrade economy comfort seats.
Airfares and flight availability constantly change --- sometimes by the minute. Because of this constant change, it is not possible for us to quote fares or to book or change flights through email (regardless whether the ticket was paid using a credit card or with SkyMiles).
For the most up-to-date and accurate fare information, please visit our website at delta.com or our worldwide reservations telephone numbers are listed on our website at www.delta.com.