I don't know that this is a fair scenario. If you walked into a car dealership and said "I want to test drive a car so I can order one through another dealer," you probably wouldn't be greeted with open arms.
This is a bad example actually. Dealers are networked and as their profit actually comes from a) manufacturer's discounts and b) service / warranty work, they will absolutely pull a car from another lot if you want it in green or with 4 headlights instead of two.
Back on topic of course...
I think the successful dive shops realize that the way consumers conduct themselves is changing. There will be people that walk into a store, plunk down a CC and make a purchase without even shopping around, there will continue to be those that don't even buy until the item they want goes on sale, and there will be those that spend 4 hours of there time and $50 worth of gas to drive to every store in a 20 mile radius to check stock and prices. These people will continue as well people that search the net and buy sight-unseen from an online retailer for "50% discount", bitch and whine when it shows up wrong size or older inventory, send it back, get another one 4 weeks later, and still think they got a deal at the price.
Not everyone considers their time, effort and travel costs as part of the sale. Nor do they consider the value a stocking retailer provides at the local level. HOWEVER, the reality is that local stocking retailers have to find a way to eke out a living in the new world of retail sales. If they can't do that, then they lose and online resellers win.
I take offense to the reseller above complaining about people coming into is store, checking size and fit and then leaving. When faced with a willing customer, who wants your product and has cash to spend; if you cannot "sell" them on the value of buying your product off the shelf while they are there, then either your sales skills suck or they were never a customer in the first place. Either way, its not the customer's fault they didn't buy at your store. They knew what they wanted, they knew what fair-market value of the item was through research and competetive shopping.
It may hurt your ego that they didn't buy, but at least they were honest with you about it. Many people would have told you they were still "browsing" and would come back later, or that they didn't like the color or whatever.
The reality is that EVERY retailer faces a situation where someone will have a product you sell, at a price you cannot afford to match, for reasons you cannot control. How you deal with this reality will speak to your long-term success in retail sales.
As a customer, My Job is to acquire the most amount of "stuff" of the highest function and quality, for the best VALUE I can find. Your's is to find out how to provide the things that I value, and am willing to part with my money for.