I flew with Air Canada last year and it was $50 can. each way , plus I had to pay $20 on one of the two trips for the duffle bag I had with me to put two panniers in. Did not have to pay that twice, which I suspect was connected to following the golden rule of Machkas final comment, arriving early and being friendly....didnt work on way back. So $120 for taking the bike, not too bad.
Did make sure that the box I got from a bike store was one of the smaller ones to be ok for the dimensions rules X by Y by Z inches.
as noted, research research research and expect a wide variation of prices.