I just got through purchasing a Nikon SB-800 flash for my camera. My current flash unit, a Nikon SB-50 DX just isn't powerful enough for the type of photography I do so I needed to upgrade to something with a bigger guide number. But this post isn't about the flash, per se.
I looked at the regular joints for my photography equipment: B&H Photo, Adorama, Cameta Camera (where I bought my D2H), Ritz, and various e-bay auctions. I don't trust the e-bay crowd all that much but sometimes you find a store that uses them as their web presence, such as Cameta.
When purchasing high price ticket items such as camera equipment, reputation is very important. You don't want to end up getting grey-market items (items purchased over seas that don't come with a mfgr. warranty) or have no recourse when you're shipped a defective item. B&H, Adorama, and Cameta all are the same in this arena (I have issues with Ritz). All three offer great products with phenomenal customer service.
So, the last bastion of choice comes down to price. Total price with shipping, insurance, state taxes (if you have such things. Us Floridians know no such beast) etc. My decision on who to buy from literally came down to an $.80 difference.
My advice to all retail sales people? Sell it as low as you possibly can. Someone else can provide the same level of service and products that you do, so your sales may come down to pennies.