Just shipped a bass to Italy, 26 lbs in a case inside a box sized 51x17x7. Cost me $105 via USPS. USPS doesn't provide enough insurance coverage so I use Shipsurance.
My USA shipping costs less by UPS because my local 'UPS store' beats the rates charged by the actual UPS facility and beats USPS also. Florida to NY for under $35 for that same size and weight box.
Those standard bass boxes are way too big, they are charging you DIMENSIONAL WEIGHT, not the actual weight. The smaller the box the less the cost. That's one of the reasons I include a case with my basses. I buy the cases from ZZounds for $79 shipped, they must get a ridiculous discount from UPS. Includes 2 boxes. One fits the case very tightly, the other is an oversize bass box. I discard the "bass box", stick some of that cardboard strategically in the case box and save enough on shipping to pay for the case vs the extra time to safely pack an uncased bass and the cost of a "bass box" that I would have to cut down to ship only the bass for a reasonable price. I figure $50 for US shipping as my cost, it evens out. Next one goes to California.
Over 50 shipped, 1 damaged.
Anyway, both UPS and USPS provide rate quotes online. Tracking is still much better with UPS.