So after his initial offer you remained silent and held eye contact, then he continued to give you a more favorable deal?

I do this every time I'm buying things with negotiable prices. My trick is to not use any eye contact until negotiation time. The surprise throws most people off their game enough to give you an advantage. Plus, it is kind of fun watching someone talk themself out of money. FYI, it doesn't work every time, typically there will be an awkward silence and I'll have to throw out an offer.