Hi, you have a common problem, but before i explain a possible way out, I must say that I'm a bit confused by the content of your post. You phoned a "USPS Store"? I'm sure you mean a UPS Store. The USPS (United States Postal Service aka US Snail) operates stations in each postal zone, they are not retail outlets to the extent that UPS Stores or FedEx Office locations are. Furthermore, unless you are an employee with access to secret numbers, connecting anyone at the US Snail by phone is something that requires papal intervention or an act of Congress.
OK, having said this:
1. It is an axiom that the US Snail will beat any of the commercial carriers regarding rates. That explains the differential in price mentioned in your post. In exchange for that bonus, you don't get the tracking reliability with the Snail service as the couriers offer. The exception is USPS Express Mail service, you get good performance but pay a premium for it. Still, for international shipping i find FedEx and UPS tracking to be tighter, but on the other hand FedEx no longer accepts weapons as stated in my prior posts.
2. You can get accurate rate quotes from the US Snail on their website calculator, at www.usps.com
. You pay the same rate for all services whether you book online or do it over-the-counter.
3. You can likewise calculate rates for commercial carriers on their websites, www.FedEx.com
. But be aware that these outfits quote different prices depending on your business status with them, and on what platform you are making your inquiry from. You'll get a certain rate as a private retail customer from the website calculator. If you have a business account and are a "volume shipper", you get a discount off the standard rate, how much depends on how much you ship per year. This amount is automatically calculated when you log in to your account before making an inquiry or purchasing service.. The WORST quotes are the ones you get on the phone or at the counter of the UPS Stores, or FedEx Offices. Those will induce real stickier shock, just as you experienced.
I guess we can chalk it up to capitalism at work. Your experience can be likened to currency exchange when traveling -- do it at the airport and you're subjecting yourself to highway robbery. Using a no-fee or low-fee credit card geared for international business travelers will save you a bundle. In other words know the market and how the players operate to choose the best, or the least painful, option for yourself. Good luck, man!