When I used to run into guys like you I also liked to charge you a little extra just to screw right back. You might be interested to know that most of the time this didn't actually put any extra money in my pocket, either.
I'm tellin' you guys, this is a losin' proposition. When you go into a parts store, they have seen YOU before. They know all about the know it alls, the "they're all the sames", the "it doesn't matter," and the "let's see just how much screwins"
If you REALLY want parts, get serious. You are wasting their time AND yours.