How do sellers on eBay make money selling cards for $1-4?

I see a ton of listings for individual cards priced between $1 and $4. Once you factor in packaging (top-loader, sleeve, bubble mailer) and shipping, that seems like it can’t possibly be profitable. Am I missing something, or is there a way this actually makes sense at that price point? Curious how people who sell in bulk or list a lot of low-value cards make the math work.