Seems to work best if you have 2 or more bags:
With airlines charging ever higher fees for the right to lose your luggage, you might find it cheaper — if not safer — to ship your bag than check it.
Airfarewatchdog put together a handy chart showing how much airlines are charging to check your bag. Most U.S. airlines want you to fork over $15 for your first bag and $25 for the second. If you’re one of those people doesn’t know the meaning of the phrase "travel light," you’re going to pay through the nose if you’ve got more than two bags or a suitcase that weighs more than 50 pounds.
With that in mind, we did a little research to see if a trip to the post office beats a trip to the airport bag drop.
Let’s say you’re headed from Boston to New York with a bag that weighs 35 pounds. If it’s too big to carry on the plane — and at 35 pounds it probably will be — you’ll shell out $15 for the privilege of checking it in. Box up your stuff and haul it to your local post office and you’ll pay $18.98 to ship it via two-day Priority Mail. UPS will charge you $20 to get it there in seven days — so plan ahead — and FedEx two-day will run you $20.88.
So far, snail mailing your luggage doesn’t seem like a bargain.
But the math changes when you throw a second suitcase into the mix. Check two bags and you’re out $40. That’s what you’ll pay to have FedEx throw your luggage around, but you’ll pay $35 using UPS and $34 to let the post office deal with it. The savings really kick in if you’re a clothes’ horse or you bought every souvenir you laid eyes on. Airlines will nail you for up to $140 if you’ve got three pieces of luggage, but the post office will charge you $55. FedEx will get it there (or back) for $60.
U.S. mail is an even bigger bargain if your bags weigh a ton — a 65-pounder costs $24 to ship parcel post, but the airlines will charge $50 and $100 to throw it in the cargo hold. The bottom line? The more stuff you’re packing, the more it makes sense to consider shipping it.