Declare the correct value on the Customs form?

+1 for curiousjim 

in fact, in general we know nothing about the actual problem with the LP, other than that it might be worth $1200 to a particular collector. By the way, valuing it at $1200 solely for the benefit that might accrue if it’s lost or damaged might equally be thought of as fraudulent by a determined moralist.

And this ’holy grail’ LP is.....well, unfortunately I do not have a copy to keep yet as this copy is being returned. I will hunt another down ’in the wild’ and can then let you know.... :-)

The Seller readily agreed he was too enthusiastic with his description. The "NM" grading and writing it was "...like new..." and so on was not the case in reality. Oh well.  Previously he has always accurately graded and described his records I bought. This was a unique blip. C’est la vie!

I assure you, you’ll have no competition from me in hunting down another copy of the LP, no matter what it may be, if the cost is anywhere north of $30. 

@vinylfun   is this a private purchase or is it an official store?
Purchased on Discogs maybe?

I wouldn't judge anyone paying $1200 for an album. It can be a time capsule, with an emotional value one can't not have. For me, a $1200 cable would make less sense...