The USPS is really poorly run and managed. They are running deep in the RED currently. They cannot seem to compete against the big carriers anymore. If you choose to ship internationally through FedEx or UPS you can be very competent that their price quote is accurate, however it will cost 2 or 3 times more, which is probably one of the many reasons why the USPS is losing money! Domestic shipping fees are about the same between the major carriers with the USPS usually the least expensive but only by a small percentage. I'm not sure why there is such a huge difference between USPS and the others on international shipping, but there is.

Another thing to consider is that time is indeed valuable. To ship domestically via USPS you can go online and pay then print the shipping label. Then all you have to do is drop off the package or let the mail carrier pick it up. Fairly quick and easy. However, with international shipping you would be ill advised to do that. You have to go wait in line at the PO while one or two of the slowest, most easily distracted USPS workers take forever waiting on the two dozen or more customers who are in line before you. It can take an hour or more to mail something internationally. USPS PO employees are widely known for being sloths, and they never have enough lanes open to handle the number of customers.

We joke that grass grow faster than PO employees move. I guess they have a good union! Any job I ever had that kind of slothfulness would have resulted in employment termination.