You are booking in the most expensive time of year. I just returned 12 days ago and paid $200 for Delta Comfort each way. But I bought my ticket in January and used 100,000 miles to reduce the price of my ticket to less than half price, $1170 with Delta Comfort. Whether a person chooses to upgrade to Delta Comfort, regardless of the price is purely a personal decision. United, and I assume all the major airlines have the equivalent of Delta Comfort. It is always up to the individual customer whether it is worth it or not.
It is my opinion that if you are paying all cash and not incorporating frequent flyer miles, it is always in your best interest to contact Travel Express or another travel agency that handles international hunters on a regular basis. If they are not able to help you, you have lost nothing but a couple of phone calls!