It would be a compete waste of money to sell your Vita to buy this. You would end up spending more money because the PS Vita goes for about $150-200 used on eBay and Craigslist. Don't forget your PS Vita is tied to your PSN account. Even IF you formatted the system, its already registered only to you and your PSN account. If you do end up selling it you might want to call Sony 1st and have them remove the system off your account.
You can deactivate a system yourself, you don't need to call Sony to do that.