uh 18 carat is nothing, it's 0.0036 kq, which is 3.6g
28g of gold round 1200, now 1200/9 = $133 against $400+ of bitcoin, not worth it
It might depend on the brand. I'm not really into jewlery and watches, but i think some brands might be worth more than their weight in gold??? Offcourse, in this case you would need a certificate or go to a good jewler to estimate the real value of the good. Which would be a hassle to do for $400.
OP, where are you from?