Whether I'm buying 2 fish or 20, I pay for no less than overnight shipping (I actually prefer same day airport to airport) and pick them up at the airlines office.
So a small package overnight (within 24 hours) is usually @ $50 (minus the cost of fish) or is around $80 airport to airport (minus cost of fish), With airport to airport, the cost is usually competitive, because a lot of fish (water weight (@9 lbs per gallon) ship for a lot less cost than even a small package with Fed Ex or even the USPS..