I don't know the details of the transaction, nor have the time to research for it (especially on RC) but I suspect what may have happened.
Dealing with the communist nations of China and/or Vietnam is an entire different ball game. Last year I screened through about twenty suppliers before finally settling on one particular firm that I felt comfortable doing business with. (I designed/engineered our own swag bags, specifically for MAX, and then had them manufactured in China)
Exploiting foreign transactions is not only a commonly accepted practice, but actually admired in their business culture. Most often the extortion is perpetrated by a 20-something newby on the other end of that keyboard who is trying to make a name for himself. This should be remembered above all as not all business decisions are final...not by a long shot.
The proper response (if my suspicions are correct) is to firmly, yet professionally, remind the Chinese contact person of the consequences involved in making demands for more money.
The old fashioned American Boycott is extremely effective, and not one that a company like Jebao would find tollerable amidst the introduction of a whole new product line to the US Market. Informing them of how many consumers they are affecting should do the trick. They may mistakely believe they are dealing with just one easy target, not an entire group of people.
A typical challenge in this scenario is that many English terms and phrases (common to us) are many times lost in translation. So conveying such a seemingly simple idea as "HEY, don't screw us over" may not be as easy as you think.
On the flip side,
should this be an honest mistake made by the group-buy organizers, I will fully support you and gladly pay whatever additional fees that are necessary (really, ten bucks won't even buy you lunch these days) but I won't bend a dime if its some schmuck sitting in a dust-filled Shanghai cubicle looking for his next pat on the back.
BTW,
if you didn't keep your MAX bag last week, you should have. It will hold about 80lbs. worth of bricks. Just don't ask how I know this, LOL!