It looks like the fare code is different. The $1,319 on ITA is booked in KLABUSIA while the $1,846 on Delta.com is booked in KHABUSIA. Someone who knows more about Delta booking codes might be able to explain the difference. Try some other 3rd party booking sites (orbitz, travelocity, expedia) and see if you can get the lower rate. If not, a good travel agent should be able to find the $1,319 price.