One important future to avert is where organized crime is rampant. Even if we look at only the economic costs, one study in Italy suggests mafia domination cost 16% of per-capita GDP. Given the US's $20 trillion GDP, that's quite a lot. And that's ignoring people's preference for security and safety. As an entrepreneur, for example, I think it's great that I don't have to worry about paying for "protection" to keep from having my business burned down or my legs broken.
We also have to look at terrorism. KYC/AML work to keep cash out of the hands of terrorists. Terrorism is, moral and human cost aside, very expensive. The 9/11 incident alone sees estimates in the $2-3 trillion range for total economic costs.
So even if KYC/AML really does cost hundreds of billions, which I doubt, it's a bargain compared to the problems it's meant to prevent.
[1] https://onlinelibrary.wiley.com/doi/abs/10.1111/ecoj.12235
[2] E.g., see https://www.brookings.edu/articles/the-world-after-911-part-... and https://archive.nytimes.com/www.nytimes.com/interactive/2011...