$1,000 plus would be fairly standard based on earlier belt tests and class costs, coupled with close to $500 for a black belt test. Indeed, they may have paid much more. Child black belts are a bit of a scam in the martial arts world, with parents sometimes paying 4-5 times for their children to test for a black belt before they leave kindergarten.
Don’t get me wrong though, the kid is adorable - especially with her cape.
This was filmed at a demo in Puerto Rico, which might put the cost for the belt lower. I know little of the martial arts scene there (and I’ll admit that).