A few extra inches difference in size can triple the cost. Weight matters too, but not nearly as much. It also matters whether you want door-to-door delivery, or whether you will take it and/or pick it up from a distribution center. For all these reasons, any estimated cost could be wildly off.
If you already have a box, measure it carefully. Then weight your bike + box. Then go the the FedEx and UPS and USPS web sites to determine a cost and how long it will take. You'll save a lot of money if you remove both wheels, but then you'll have to pack it more carefully.