Here's some more realistic prices on shipping (From Central USA to Sydney, Australia):

USPS Priority Mail® International Large Flat Rate Box  23-11/16" x 11-3/4" x 3" - $60 and it's flatrate. All 3 cards can fit into this box AND have sufficient packing.

I don't have exact dimensions of a 5850. If it's less than 10 inches, 3 probably could fit in a 11" x 8-1/2" x 5-1/2" Priority Mail® International Medium Flat Rate Box for $47.95 shipped.

These boxes are free, just need to use cardboard to fill in the spaces. Remember it's the impact of the contents shifting around that damages the stuff. You pack it all in tight enough, it's fine. You don't need a foot of packing peanuts around it all to keep the stuff safe.