Thanks for the tip! It's mostly PayPal that takes a share, MakerBot bundles the tips in a monthly pay-out to reduce the share lost per transaction.
The butterfly could be rather easily improved by adding some extra material to the outer ring of each hinge, which is the weakest part. There is no reason to flatten this part, because it has to rotate around the axle anyway. I had a quick go at this for one hinge, but doing it for the entire model will require a few hours of tweaking and fiddling. I might do it someday if I find the time.