Actually they do write tickets in private parking lots because this happened to me and the cop was right there when it happened, he just pulled up and aksed did I want to file a report. I told him no since the guy had insurance but he gave me copies of the report form anyway just in case. I would give the guy one more shot and tell him that if he doesn't want to pay up then you will get insurance and the cops involved, and that means higher rates for him and possibly points on his license if you take it all the way to court. You wanna be nice cause if it happens to you then you would want someone to be nice but it doesn't always work out that way.
My thing is, if he owns the local pharmacy (and we know how expensive medicine is) then why doesn't he just pay up and forget about it? If he was cheap then just take the lower estimate and be done with it? People are so crazy sometimes...