In that case, I'm a little confused, because you did seek out and find cheaper shipping options for your What's O.L.D. is N.E.W. Kickstarter - which was a key deciding factor in my decision to back it.
Like everyone else, I made an (educated) guess as to what the international shipping costs would be a year from now, and like you say, looking at different shipping options does allow for some control in that regard. There's never a guarantee, though (and those shipping costs still weren't exactly low!)
So no, it's not completely random. You can make reasonable guesses, which is why we're able to and have done it. If you couldn't, then KS would be dead in the water, at least for any international shipping.
I know of at least one (major) Kickstarter which lost money on the shipping by guessing wrong. It does happen, and not just to inexperienced people.