How does refraining from collecting sales tax make Amazon look cheaper than Barnes and Noble? The sticker price doesn't factor in the sales tax; on an item-by-item comparison, the prices would look the same if B&N could match Amazon.
Based on this observation, I find the explanation that Amazon's not interested in spending the money to track state and local sales tax policies to be more plausible.
I don't think sticker price comes into play as much online. If you buy enough online, you get accustom to going through the purchasing process due to the additional price of shipping.
If B&N is calculating "Shipping + Tax" while Amazon is just calculating "Shipping" there will be a slight difference in price. And why not go with the cheapest?
Based on this observation, I find the explanation that Amazon's not interested in spending the money to track state and local sales tax policies to be more plausible.