one way car rentals can be very expensive. I had to do this a bunch of time while traveling on business. The reason why it's expensive is because they car rental company that owns that car has to pay someone to drive that all the way back.
So you technically pay for the rental down and they for someone to come down and drive it back. It get's really expensive. Trust me
1 way airline tickets are easy. Just purchase the 1 way and not roundtrip