Rods, even spey sized ones from the UK to US/CAN are normally between £30-£50, using a broker like Interparcel. Much higher via the couriers like DHL, FedEx directly, even though the broker also uses these couriers. Obviously insurance adds much to that figure depending on how much you take out.
The other direction is high, as a dispute between USPS and Royal Mail a few years back means that you can't insure anything of value more than about $80, but the cost is relatively low, around $80. Via courier, it's astronomical in the longer sizes over 1m, something like $200-$300! A glass rod finisher I had make me a rod some years back vowed never to send 2 piece rods again to the UK after my episode. In the end I took a roll of the dice and he sent it with no insurance, but it got here safely. Sweated buckets for a couple of weeks though.
When returning a rod to a manufacturer abroad, the rod should be marked "Warranty repair only, zero commercial value", and also on return to you, or duty/vat will be charged to the receiver on both sides. Proof of sending, emails, etc will need to be produced otherwise claims for refund will not be successful.