I used to say all sales final, but then I got into people just completely ignoring that and filing claims with paypal for buyers remorse
So, now I have a 30% restocking fee and I don't refund shipping (it's steep I know, but it makes people think twice about buyers remorse), I also put a tyvek wristband with my ebay name and "must be attached for return" written on it and I attache it somewhere where it cannot be tucked in or removed which takes away the worry of bait and switch
it's a tough policy, but it seems to work and I've made a tidy profit on people returning stuff. If they want to return it that badly, I'm taking 30%.
Hope that helps. I'm a silver powerseller with over 500 fb and most of that is selling.