Its been a while, but I've never had to pay to fly with a bike (Air Canada/Quantas). I agree about the small airports bit. Don't use cardboard if you can avoid it... a friend's bike arrived with footprints on it. If you can talk to the people at special services, quite often they will let your bike go unboxed. Some bagage handlers apparently prefer it that way.

Another tip: If you are crossing any borders, you can save time by washing your bike before you leave home. Customs people are quite concerned with things like hoof and mouth disease being carried by the dirt on your bike. I spent an extra half hour at Cairns Airport learning this the hard way.