The cost is subject to a number of variables, and a constant, accurate figure is not possible. Utilize a travel agency or online flight search engine to get an estimate.
You don't specify from where, and even if you had airline prices vary widely depending on many factors. Your best bet is to go to a travel website like orbitz or travelocity, put in the travel dates,...
From Australia, on a school exchange (keep in mind this was two weeks of 'free' homestay and one week of expensive hotels --> going to HOSTELS is cheaper by a lot), it cost me ~$4400 without...