USPS SHIPPING OVERSEAS
I just wanted to write a few words for all of you who are thinking whether to sell/ship overseas.
I have just bought a UMC-200 from a user who has been kind enough to ship it to Madrid-Spain. While the estimated cost was more than $300 using FedEx, USPS quoted $125 including insurance for $500 value. In fact, USPS matched the delivery date, and the delays afterwards were due to local customs/postal service err on the documents numbers.
Anyway, the important thing is that it arrived perfectly, except for a knock on the exterior box, hence the importance of double boxing. It took from march 8th to march 15th (seven days, quite nice).
So, my advice, is:
1. Yes, you can use USPS priority mail to ship overseas. It will travel by plane.
2. Make sure your customer is aware of customs regulations. I knew in advance I would have to pay VAT+Customs. That will be valid for all European countries in the EU. If they fail to do their duty, there is a chance you get your item back. So, be sure to keep track of crossed mails, etc, to avoid Paypal claims.
3. Use double boxing! And, of course, use the insurance for a fair value. Avoiding costs this way may prove a bad idea.
I want also to thank the user @hmthtrnut who has been kind enough to ship my (brand new) Emotiva UMC-200.