system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do so many concert venues charge an extra couple of dollars for people who are under 21?
gpt
Alcohol sales count for a huge amount of the expected revenue for shows, young kids are sometimes taxed more for not being able to contribute to the bottom line. 

If they had sold that ticket to someone of age, it's a safer bet they will be spending more money at the venue than someone under 21.