I used the original invoice, so obviously there was a risk on my part because the sale amount was considerably more.. but there's always going to be a danger in shipping one of these (if it gets lost/broken etc). Problem is that if something does happen and you insure it for the full sale amount, how would you prove its value to the carrier for a claim. If you sell on eBay, you could. If you sell on here for BTC, you can't.
I think we could in the UK - HMRC is currently classifying it like face value cash vouchers. Might be messy and need some legal force, but could be done.
I expect you're correct. Very messy though.
I just had my fingers crossed from the moment UPS collected to the moment they delivered, that worked for me. Probably the same kind of advice you'd get from your spiritual guide above.