Why can't you use penny sleeves or put 3 cards in a top loader and ship in a A3 envelope which would be cheape?
Delivery confirmation cost $1.25. The buyer doesn't have to pay this fee. Also by shipping in a padded envelope no cards will not be damaged by the rough handling of mail by some USPS employee.
**The USPS retuned to me a half padded envelope with the cards and a torn invoice in another yellow envelope with a apology for damaging the mail. I had to pay shipping again no cost to the buyer. The buyer did receive a tracking number for the first and second packaged.**