I've been listing a lot of cards at $2, $3, $4 (free shipping)- some of them even sell!
I mail those in a top loader and PWE. I also state that I will do so in the descriptions.
When I receive feedback, it's typically within less than a week after mailing.
I've sold dozens (maybe 120 or so) since last fall. Only twice has anyone contacted me saying they didn't receive the card.
first time was in January and I also had several more expensive cards out with tracking, so I was able to report that I had a couple that spent 4 or 5 weeks of postal travel and finally arrived. So, I asked the person to give it 4 or 5 weeks. That one finally arrived.
second time was recently.... I asked that person to give it 4 or 5 weeks and if it doesn't arrive I will happily refund. I need to check in with them
Haven't had any not show up yet, knock on wood.
I only use PWE on amounts I wouldn't mind losing and would not argue about a refund.