I would pay the refund and end the matter asap. I know a lot of people will not agree with that, but basically it is a second hand camera and the warranty is NOT transferable so you are lucky he's only asking for $150. I'm not saying you did anything wrong, I'm just saying that for me, an end to the hassle would be worth the $150. Otherwise this will go on and on.......and on and on.......and on.