well anything you want to receive overnight is not cheap. Aquabid's got some good deals too but shipping is pretty even just about everywhere for shipping.
As for the shipping costs, find some people near you that might want to do a group buy or wait to buy a bunch of species at once so its a better deal.
If you get really small fish sometimes they can be sent via priority flat rate boxes which is a little cheaper but you might lose the fish so a lot of sellers don't guarantee those unless you are close.