system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly are taxi cab medallions and why are they so expensive?
gpt
Taxi Cab Medallions are just the name given to the license to operate purchased from the city.  They were, likely, actual physical medallions to be displayed at one point.

The reason why they're so expensive is because they can be.  The city limits the number of cabs that can be in operation for a variety of reasons (some is pure greed, some is traffic management, some is random bureaucratic nonsense).  As such, there's a very limited number of medallions available, and you literally can't be a cab without one.  The city can really charge whatever the want for them, but if the price is too high, then nobody would buy.  So they're generally priced to be high enough that the city gets a lot of money, but low enough that cabs can actually be profitable, and thus the medallions will be bought.