Do not send anything without tracking that would cost you "too much" to lose.
Your 99c + $3.00 shipping cards fit in that category.
I assume you pay less than $3.99 for your cards.
What you need is Cookie Jar Insurance.
This is just setting aside a few virtual pennies in a virtual Cookie Jar as self-insurance premiums against occasional problems. Not just scammers, but loss in transit, honest returns, and your own errors.
When you have to refund, you use the virtual money in the Cookie Jar.
Now for the scammer, whose name has already been removed from your post, Report him to eBay
The phone reps do not work for eBay so don't bother with them. They work for a subcontractor out of Utah.
https://www.facebook.com/eBayForBusiness/ — Message button in upper right on landing page.
https://twitter.com/askebay?lang=en
https://community.ebay.com/t5/Selling/How-do-I-contact-Customer-Support/m-p/32016431#M1783851 -> Automated Assistant, type AGENT -> enter. You will then get more options.
The social media Chat accounts are covered by trained eBay employees with some authority.
And you get a transcript so you can compare what you heard with what you were told.
Have all those other sellers do the same.
EBay will not act on a single member's report, but if they are getting several Reports they will.
Block him on your own account.
And set up your Seller Preferences/Buyer Requirements to automatically Block any buyer with Strikes for Unpaid Items. This will filter out a lot of Bad Buyers before they can even bid.
