a little ad etiquette II,pointers to being a better potential buyer

I like this thread-Just had a potential buyer,we talked on the phone- emailed-I came down on the price,got everything set up so that he had no shipping,I pulled the trans off the engine loaded it in the back of my truck,tied it down hooked up the trailer,called the guy I was buying other parts from, set up time to pick them up.Then I get a call from this guy and now all he wants is a 10.00 part.Yeah I have had my share!!!