Unless you're in the UK, you might not get this joke. As of this year, supermarkets and lots of shops have to charge us 5p (or about 3 cents) per carrier bag. That's an awful lot of revenue if you bag all your weekly shopping with these things.
The 5p charge has caused an awful lot of contention here as they won't use paper ones. So we now use our own re-usable bags to avoid the 5p charge.