I work with ex-PayPal engineers on similar systems. While I can't give numbers as they're confidential, our automated systems catch a lot of attempted fraud, and I know Paypal does far more payment volume and has much more sophisticated fraud detection systems than us (compare three years of data to over a decade at scale). Doing the math... yes, it's a lot.

Also, fraudsters tend to not brag about how much fraud they weren't able to process.