I'll have to chime in on this one. I shop at several local stores, and have good business relationships with all but one in my area. (And that guy has serious issues with many of our local divers.) I also buy from shops in Florida when I am down there on business. Furthermore, I pick up items from time to time on ebay and other online resources.
I visit dive shops often, and rarely leave without buying something. I try on gear, test new equipment, borrow DVDs, hang around the shops, drink beer with the staff and the end of the day, etc. None of these activities creates an obligation, either expressed or implied, that I will buy exclusively from any particular shop. Until I place an order for a piece of gear, I'm still out there in the marketplace, looking for information and a good deal.
Any sales professional knows that the deal isn't done until it's closed and the money and goods have changed hands. A good sales professional knows that it's not over then, as good customer support generates the kind of loyalty that the shop owner in the original post was trying to coerce out of our shopper.
I worked in sales for a large pharmaceutical research company for 4 years. During that time, I made many multimillion dollar sales. Did people take advantage of me from time to time? Of course. I can't tell you how many evenings I entertained potential clients with no tangible results, but I realized very early that you have to always act as a professional. As a result, I had over 85% of my business in my last year from repeat customers. My job became very easy. As for the folks who just wanted those free meals at fancy restaurants, well let's just say that on the third strike they were out. And during the second encounter, I always made it clear that we needed to do some actual business to keep our relationship fair. There's nothing wrong with asking for a sale, but you can't be coercive or rude. It sounds like our LDS owner (and some of our users) have a lot to learn.
The customer owes you nothing. Not now, and not after you give your pitch. It's your job to close the deal and keep the door open for continued business. Do it right, and you've built your market. People will naturally gravitate to your shop. Do it wrong, and you'll find the marketplace to be a very hostile place indeed.
-Grier