I imagine the $600 is the replacement cost value to DJI rather than the price you paid as DJI will be paying the custom charges.If you know the Chinese, they will tell customs they're only $1,000 when they bring them into America. Then after the 125% tarrif, they will still be $2,600. When I just paid $1,250 for my replacement Mavic 3 pro, the paperwork that came with it said it was $600! I'm not kidding.
I really can't see US customs allowing Chinese containers full of brand new Mavic 4 Pro's entering into the country destined for retail shops with a custom value way below their actual cost value.