Are miles included? Even for a non-1-way trip, that's a great price. However, the general goal is to minimize the one-way portion. If you'll be hanging around PWM a while, it might be best to break it down to PWM-PWM and then a separate PWM-LGA rental.
I've even done 3 rentals instead of a single to lower the cost: AAA-AAA, AAA-BBB (1 day rental only), BBB-BBB.. just depends on how may days you'll plan to be at each spot, or if you won't be near the pickup location at all mid-trip.