I say keep the $300 and sleep well at night. Nobody has the right to abuse you when you clearly didn't do anything other than stick to your word. Whilst strictly speaking you should hand back the deposit money, by keeping it he might think twice next time. If he runs a business and wants to be known for his good name, perhaps he will think twice before abusing people. Bullies and brash salesmen need to be taught a lesson, nothing better than a $300 lesson, other than a $400 one!