That's ridiculous!.. IF I was going to upgrade (and I'm almost certainly not) I would sell on ebay or possibly gumtree (not sure if that's an international thing so if not it's like craigslist).
I have sold expensive things on ebay before, and not had a problem. it is quite nerve wracking though!
Yes I sold my brand new Surface 2 on eBay for more than it was worth in the shops... some strange people out there.
Gumtree is in the UK too, but because it's free you tend to get 'dodgy' adverts on there; it's best avoided to be honest!