Yes I sold my brand new Surface 2 on eBay for more than it was worth in the shops... some strange people out there.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!
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!