I have never done this before with shipping to Asia. I know there is a risk of losing and custom tax. Who will be responsible for.

 

Depends on the agreement between the seller and buyer. Usually customs tax is on the buyer, but sometimes the seller agrees to pick it up (and of course it gets reflected in the selling price, so ultimately buyer pays it anyway). I do not understand the 'risk of losing' statement, though.

Also, it would help if you indicate the country the item would be shipped from.

(BTW, a 'hello', 'please' and 'think you' are always nice from a first-time poster who is asking for information )

 

The buyer pays the tax in the country they are in.

I have never heard of seller paying tax for someone else.

They pay you what you want, you ship it any fees or taxes are theirs.
They refuse the customs tax you refund them when the watch comes back to you.

 

Risk of losing can be mitigated by insurance.

Customs duties is statutorily the responsibility of buyer/importer regardless of which country. And each country has different rules on what values are taxed and at what rate. Like my country: anything below Php10,000 or about 190usd (including shipping) is tax and duty free. Watches (above 190usd) are taxed as follows: 12% vat on entire value and 5% customs duties (so including other miscellaneous charges, I estimate an additional 18% whenever i buy a watch online with a price plus shipping above Usd190).

 

buyer is responsible for all that. i would not mark down the value for the tax/custom reason if it's something valuable.
I once lost a 10k $ worth camera/lens shipped to asia and since i marked it down to minimal value (500$) to help the buyer, i took the hit from the insurance.