Actual cost is 80c. Here is the rate sheet.
There are no premiums for oversize etc. You can get a chip in a flip in a bubble mailer for that rate. If they are PS or Chipco's you can get two in there, so its not much more expensive than domestic.

Also not listed on the sheet below are the global priority flat rate envelopes. The small one costs $5 and the larger one $9. Tight fit but you can get 48 chips in a small one and if you push your luck you can fit a white PS box in the large one