I print labels out from the computer, cut them out, and laminate them with standard "ID card" size pockets.
The expense initially involved buying a small laminating machine, and the pockets. I already had a computer and printer.
I decided to add on to my labels some quick information about the plant like when it usually flowers, how much light it should get, whether it can be placed in the cooler part of the greenhouse or needs to be in the warmer part, etc.
The one thing you can't do when you laminate the label is add information about when you fertilized it last or when it last flowered but I log that separately.
The rubber band method you see attaching the label to the pot (simple hole punch) is NOT working so well as the rubber band begins to deteriorate after a few months. I am slowly replacing them with coated green plant wire