Here’s a nice article on that that free dye pack works. I’ve never heard of a bank charging for one, they give them to robbers as lagniappe, as a Cajun might say.
https://science.howstuffworks.com/question671.htm
Years ago, I remember an item on one of Paul Harvey’s broadcasts, citing an unsuccessful bank robber in Minneapolis. He decided to stage a stick up in winter, on foot. Pointed a gun at a teller and demanded money; she complied and the robber grabbed his loot and fled on foot. As he strolled away from the crime scene, he noticed the dye pack in the bag with the money. For reasons unknown, the robber decided to stuff the dye pack down his pants. It promptly exploded and blew his trousers off. It was pretty easy for the cops to catch him; he was the only guy on the street who was naked (and purple) from the waist down, fanning himself, with his money bag lying on the sidewalk.