You could also try other rental companies and see if they have a lower one way fee. I was fortunate one time as I was returning a car to JFK with no one way charge (I was told later that at that time, that particular rental car company had trouble with inventory at JFK as they had many one way rentals leaving JFK). But if you are dropping of in a more rural area, might be tough.
Or is it possible to break the rental up and use a train (or other public transport) somewhere in between. That way if you have an one-way, the drop off fee should be lower.