XL Airways, which went bankrupt in 2008 but seems to be alive again, is offering Fall 2016 travel at very low prices. In 2008 it was a British airline, now it brands itself as a French airline.
The Secret Flying website lists $451, the XL website lists $484, for NYC departures.
The XL Airways site lists departures from NYC, Miami, Los Angeles and San Francisco. The airline flies to a variety of European cities.
Your carry-on baggage allowance is only 11 pounds, of which a typical roll-aboard will take up most. A gym bag made of ripstop nylon weighs only a couple of ounces, so it would be a good substitute. Also consider carrying your electronics and other heavier items onboard in a Scotte vest.
I recommend paying with a credit card if you go for this deal, so you can get a refund if XL goes under again.