As mentioned, you need to decide the dollar amount threshhold at which you are willing to gamble without delivery confirmation. If you are going to ask even people buying ten cent cards to pay $15 for tracking, you'll never sell any via ebay.
Most people draw the line at $30 or $40: anything over those amounts that is being paid via PayPal require delivery confirmation at a cost of $xx.xx and anything under those amounts costs $x.xx and they're willing to risk the chance that the card may not arrive and they leave themselves susceptible to a chargeback.
Previews: Oilers Champ Box Set*, Red Wings 100th, Blackhawks 100th