In my case, the tickets to Europe were $200 less than the Delta price booked on the Delta website. The Delta price, however, included no change fees and if you decided to cancel your flight, you would receive an e-credit. The Air2Sea pricing includes changes up to the day that you pay in full for your cruise, after that, it costs $200 to make changes. Also, I have read from other passengers that when their flight changed they had to call Air2Sea for help, the airline refused to work with them because they had not purchased their tickets directly from the airline.
You have to consider all of these factors before making a final decision as to how you want to buy your airline tickets. Although Air2Sea was the best deal for me in regards to Europe, when I called them asking for a quote on a flight back from my upcoming repo cruise in which I needed only a one-way return ticket, I was quoted a higher fare than what I was seeing online on various airline's websites, so I booked my one-way ticket on an airline's website and I am very happy with the savings and the fact that I was also able to choose my seats for an additional fee.