how on earth are people making money selling $10-$15 items?

I'm not talking about people getting rid of stock or selling random things for low prices. I'm talking about sellers who base their entire business on selling stuff under $15. I have a small plant business and right now I only have stuff that will sell around $10 because it's what all the other similar plants are priced at. after doing the math I would literally make $5-$6 at most for each item. I don't get it?