I agree, the situation with one-way v. return tickets seems stupid. I have a similar situation with EWR-LHR on Virgin Atlantic. One way is 635 sterling but return is GBP 444. I'm buying the return ticket and not using the second leg. Saving USD 300, especially with the exchange rates, for a return I will abandon makes economic sense for this traveler. I don't understand it fromt the aircarrier's side of the equation.
As to not using your outbound ticket and trying only to keep the return will result in great disappointment to you. Others have noted this as well. Sorry for the bad news!