Per the Flight Deal there is an awesome sale to Istanbul, Turkey from major US hubs – Chicago, Washington D.C and Boston.
The deal is valid for travel on outbound from January, 2015 – March 27th, 2015. Must purchase at least three days in advance of departure. You can check the ITA Matrix for far availability.
I did a sample search for travel in March for a 5-night stay and here are the results –
You can also use another powerful travel tool Google Flights to perform a similar search and here are the results
You can get to Turkey next year for a really decent fare of under $600. I am not sure how long these fares would last so you may want to act on it NOW!!. You can also consider applying for one of my favorite travel rewards credit card the Barclaycard Arrival Plus Mastercard and earn $440 towards travel credit which could help you bring the cost of the travel tickets further down.