Our local post office here in NJ considers anything other than paper in an envelope as a "package" and will charge postage due on the package rate if you were to mail something like that to me.... thin bubble packs, regular envelopes with rigid items, etc.

As for discounts, I would highly recommend using Pirateship.com for the best rates and cheap reliable insurance for all USPS packages. They also now offer discount rates on USPS packages too. They use Shipinsurance for added insurance when needed and Pirateship.com will handle the claims for you if you have a problem. They have new international package rates using Asendia to forward internationally and then forward it via the local postal system in the destination country. Cuts costs drastically for all international packages.