Based on my 3 watch acquisition at past, there were taxed 5% (of ur declared value if lucky, or based on custom real value) + processing fees.
The custom is likely open the parcel, when the watch is send with box. They will do a quick internet search and find out the watch value .... In any case if you under report the parcel value, the custom will upscale the value to market price and tax you 5% based on the new value. Any dispute of value, you are required to provide the payment evidence / purchase receipt to custom / Fedex / DHL. Same principal applied to any watches send to oversea for Return & Repair.
For those kena 5% of declared value, you are the lucky one...