Well, now I've mailed stuff from the post office in Mexico, and I've mailed stuff from the post office here in the USA. The verdict: USPS is cheaper, easier, and more efficient. I just mailed my Mexican hammock and my runners back home, from here in San Francisco. About double the weight of the package that I mailed from San Cristóbal, and about 80% of the price (yes, mail-by-ship is an option here). And none of the box-and-packing rubbish that I had to go through in Mexico, either. I take my hat off to you, USPS.