As others have mentioned, an LDS will likely have a higher price, but with that higher price, usually come several "intangibles". My LDS also organizes trips. Not only does this mean that I will be traveling with friends that I have met through the LDS. It also means that once when I was on a Live Aboard and had minor gear issues, because I was traveling with the LDS where I bought that gear from, he borrowed some tools from the boat and fixed my problem on the spot. If I had bought that same piece of gear online, he would have had no incentive to do a quick on the spot repair for me. (Knowing him, he probably would have, but he would have had no obligation to.)
Another intangible is when the LDS is able to provide advice that you would not get from an online vendor. More than once, the owner of my LDS has "shifted" me from an expensive purchase to a more economical model that would actually meet my needs better. The online vendor will simply ship out your purchase (even if it won't meet your needs) as soon as your credit card is authorized.
Make no mistake, I also shop online. This especially applies to "niche items" such as underwater photo gear. There is no way that an LDS can carry housings to fit every camera, and the time lag between ordering and delivery can be pretty long. For most items, however, I will look at the price of the item online (factoring in the shipping cost, exchange rate, duty & taxes), and then go into the LDS and say here is what the cost will be if I order it online. What is the best that you can do. More often than not, my LDS will come up with a solution that will make it worth it for me to support him rather than buy online. Does he meet (or beat) the online price? No, he usually doesn't, but that is where those intangibles come into play.