Frogbear ... there is an image at the top of the KickStarter that shows the total amount you need to pledge to get one of everything that is currently unlocked for purchase. I'll post it here after my text.
This image will be at the top of the KickStarter and will be updated after each Stretch Goal is reached.
To answer your question ... $3 extra for international shipping once no matter how much you get.
As stretch goals are reached ... some will be free and some you'll need to add on. So right now if you wanted everything and wanted to pledge ahead of time to get Stretch Goal #2 ... that would be the $38 from the below image + $8 for Stretch Goal #2 which is not yet unlocked ... so $46 total.
When we unlock Stretch Goal #3 or any goal after #3, then you need to update your pledge to add in that new figure if it costs money to add it on and you want it. (there will be stretch goals that will be free add-ons for you).
You pledge the full amount ... there is not a bill for the add-ons that is sent at the end of the KickStarter. The add-ons are created to help the KickStarter keep getting higher and higher overall totals which help unlock more and more add-ons. If was done with a bill system, then the overall total wouldn't reflect the money raised and it would not be as easy as KickStarter/Amazon taking about 10% of the total as soon as the KickStarter is over.
I hope this helps ... if not please feel free to ask more questions!
Tom @ Impact!