When I do go back to selling on eBay, I plan to remove GSP and instead offer direct shipping to the buyer using FedEx International Priority. I have a duties calculator provided by easyship.com that gives reasonably close duties estimates. I do not want to use USPS since I paid for their fastest service (Express Int'l) only to have the item sit in chicago for an entire month before it moved again to to buyer's... Source: over 3 years ago

As for the cardboard, it's easy to recycle, pretty efficiently. Plus you might look into this program: Https://givebackbox.com/amazon. Source: over 1 year ago

Do you think the item is in good enough condition to give to a friend for free? -- Try giving your items to friends and family. Otherwise, set the item at the end of your driveway and post it to Nextdoor and/or a Freecycle group on Facebook. If donating would make you feel better by helping someone else, take it to Goodwill, Savers, Salvation Army, a local library, a school, etc. Some donation centers even pick up... Source: about 2 years ago

At first, I thought OP's mention of "donation boxes" were actually these Give Back Boxes which would be filled with people's used items, but then OP clarified it to be mostly private label Chinese goods which makes more sense. Source: over 2 years ago