To a bit on why the cost is so different. It’s because that plane is flying overnight packages no matter what, it could be half full, 80%, or totally full. That forces the price of overnight to always be able to cover the flight. 2 day packages can allow for planes to run full more often or get placed on trucks. Since it costs negligibly more to fun a full plane than a half full plane, the 2 day packages don’t need to cover the same amount of costs.