I sent 6 bags MBag, the cheapest economy and it was $144 for all of them. Weight maxes out at 44 lbs. You can go to the post office and ask about it. They will quote it all ways - air, ground and what I now affectionately refer to as the slow boat. I received my first MBag here within 6 weeks, 2nd bag showed up 2 days later. Still waiting on 4 more bags to show up.
I wrapped each book in plastic wrap and then boxed it. Box was then labeled with my address here and marked "postage paid MBag". The customs form is filled out and attached to the MBag. When you go to the post office, they will give you the tags and such that need to be attached to the bag.
I have been very pleased with the result so far. The bags looked pretty tattered but the boxes were just fine.
~BEG