When you have to take the neck off of the body, buy bubble wrap, bubble wrap the neck and body, find a box to fit the body and neck in ....that is "going out of the way" as opposed to just leaving it assembled and shipping it in a case. I also had to cut a box down twice because of size restrictions, which equals multiple trips to the post office.
Isnt this the reason that there is an International For Sale section in the classifieds?
I have shipped basses all over the world and have bought basses from all over the world and have never had to alter the way i pack a bass. It's the same if it's local or international and my basses get to where they need to go within a week, anywhere in the world (i use DHL).
From what i understand USPS bought in some size restrictions, so don't use USPS. Use FEDEX, UPS, DHL etc. The buyer covers shipping costs so only offer these couriers, if they don't want to pay $300 shipping then no deal.