Retail sales in general isn't easy. Especially nowadays with online vendors, money being tight, and people always looking to feel like they are being treated special. I worked in a family retail shop when I was in HS and a little while in college and while it was fun, you definitely have "those customers".
While that experience has made me more understanding of those who choose to work in retail, there's NO excuse for disrespecting your customers. Yeah, you are probably right in principle, but in my case, they weren't following their written policy as stated on their website. It's not like I was trying to be difficult or anything like that. I was ok with the whole situation until the person in the shop tried to make a point that he was "technically" right and they have a right to charge that price. Well, you have every right to do so, but you should clean up your stated policy.
In general, when I go into a LGS, I know exactly what I want. While I do occasionally look around, check things out, etc, it's not that often. I am respectful that their time is valuable. That said, see how far you get without customers.