That threshold has not always been there. Used to be 20k, but they had to lower it to catch the billionaires.
https://www.wolterskluwer.com/en/expert-insights/irs-delays-...
https://www.wolterskluwer.com/en/expert-insights/irs-delays-...
So it applies to digital payment methods like Paypal, to payment networks like Western Union, but also to any credit card transaction over $600?
edit: I think I was thinking of the payments in the wrong direction. The 1099-K applies primarily to the receiving party?