WOW Air offers Air Travel from Select US Cities to Iceland: One Way Flights from $99 or Round Trip Flights from $149.99 when you travel on specific dates.
Note, you may also use Expedia Orbitz or Priceline or if you think you may cancel within 24 hours. While fare is valid at time of posting, fares can fluctuate in a matter of minutes/hours/days.
Example travel availability:
Boston (BOS) and Washington, DC (BWI): Mid January - Early May 2017
Los Angeles (LAX): Early February - End of May 2017
WOW Air also offers One Way Flights from Select US Cities to Paris, Amsterdam and London from $149.99 when you travel on specific dates. International flights will make a stop in Iceland.
https://wowair.us