You might be able to use a freight service with an 80lb item. Cost can vary depending on where you are located and where it is going. I can't say for sure most pallets and freight I get are 400 to 600 pounds. Not sure if 80lbs is enough but like I said lots of factors.
You don't say what the item is but you might try a common carrier or trucking company. Is it possible to make 2 shipments and send USPS if fits the size requirements?