If you use Fedex for example: you have to specify 2 prices: the declared value (it's up to you to indicate 0, as a gift, but risky IMHO) and the insurance value if you want one.
Of course, both prices must be coherent... customs are not stupid and they look at that.
Tva will be calculated from the declared value.
The worst case is: you declare a "book", as a gift, at 0, and insurance at 5000...
This is a big warning for the custom, and you can be sure your parcel will be opened.
I know it happens... (I have a friend who works in Roissy, at french customs...)
I sometimes make a deal with the seller, but I take a risk: I send 1000 to the seller, ask him to declare 500 and insure at 500. For a vintage watch, price is very very linked to condition, so, it can work, I usually ask the seller to indicate that the watch is without any garantee and needs a repairing service. I don't know if it helps, but again, it is a "possible and usual" case. For a brand new watch... I don't play of course... Again, customs have internet, they know the watch market, they know ch24. Easy to find a market price for a new watch.
Of course you can be a real player, declare a Rolex as a "book", as a gift, with no insurance. It can work... All parcels are not opened...
Anyway, fully agree with
@STANDY : it is on the buyer side...