Free: Contests & Raffles.
You can make a tube out of PVC pipe to fit your rods exactly pretty easily. Just put an end cap on one end and a threaded cap on the other.
Alaska Airlines used to let you check one piece of sporting equipment for free but they don't anymore. Fishing rods could get pretty expensive if you don't have free bags somehow. I've built several PVC tubes for Alaska, even the baggage handlers can't damage those. I'm pretty sure you could drive the plane over them.