Here is an example of the sales tax issue. On B&H Photo the Nikon AF-S DX 17-55mm lens is $1,259.95 plus Los Angeles County sales tax of 9.75% equals an additional $122.85. Not to mention the fact that Samys Camera quoted me $1,399.95 for the lens plus $136.50 sales tax.
B&H Photo Web Site $1,259.95 No Sales Tax and FREE SHIPPING
Samys Camera $1,536.45 Including Sales Tax Shipping N/A
This is a difference of $276.50 that I am not willing to pay to support a local merchant and I do not think that most other people are as well. This difference could be used for another low price lens.
Samys Camera does from time to time have a no sales tax sale, but B&H Photo is still less cost on the lens it self.