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I agree with you that it is not large, but there are not many larger markets that are worth more than $200 billion that are completely unregulated. There are some, but not many.

The only thing that comes up to my mind are illegal drug markets. I went on a search and found this. Counter fitting 1 trillion, drug trafficing 500 billion.

https://www.talkingdrugs.org/report-global-illegal-drug-trade-valued-at-around-half-a-trillion-dollars

Crypto would be third in the list. Quite amazing.