Although I cannot find the URL, I recall reading somewhere that, on average, Amazon prices were 9% lower than big boxes' (BBY, et al). not clear whether that was 'bottom line' price comparison (in which case AZN's prices would not include tax whereas brick & mortars' would. Now that AZN agreed to collect sales taxes for a number of states that delta will shrink.

But, I do believe that convenience of easy ordering (for lazy ppl like me), is bigger differentiator than a couple of percentage points on pricing.

And that's just generic products on Amazon. As you get more specialized, the price at most brick and mortar stores seems to keep increasing more and more, whereas the prices online remain consistently low.

Infrared LED at Radio Shack? They wanted something like $6 per LED. You'll find the same part online for pennies.