Depends on the type of sticker. They sell big stickers individually in a lot of places and some places have custom-made specialized stickers which they will sell individually.
When I was a kid, there was a kiosk in the mall that had dozens of sticker rolls and you could pull off as many as you liked from any roll you wanted and buy them. That was awesome.
I'm guessing that's exactly how they do it. But they still sell them individually to their customers. The customers seem willing to pay or they wouldn't keep selling them.
You also have situations like a band selling a sticker. They're not going to sell you a roll of stickers.
I still don’t think you’re getting this. The band buys in bulk. The fan buys the single sticker.
Fans can order the same sticker off the internet in bulk by uploading the motive to a copyshop. What's there not to understand? Did you even read what you posted here? It's about the anxiety where to put a single sticker. And that is gone when you just scan and upload the motive to a copyshop and order a stack for peanuts.