As of the current moment, there is no other use for the golden balls.
The description seems to just say that the item shop will take it for "a lot" (50k per may or may not exactly be a lot though...) so the likely best option would be to indeed sell them as it implies that there will be no other real use for them even in the future.
Alternatively, you can hoard them just to show others that you've ripped out a lot of golden balls.
Connect With Us