In my opinion, no one who is unwilling to help a fellow cyclist belongs in a bike shop. I don't know of anywhere that pays mechanics on comission, so I don't think that making a few extra dollars should be a concern. Of course, I don't really think that anyone who is unwilling to help a fellow human being really belongs anywhere, so I don't know that this specific opinion really helps... I worked as a mechanic for a long time, and unless I was super busy I never minded giving advice.