An NYT article on the battle between Amazon and Hachette, a major publisher, told readers that:
"Thanks to Wall Street’s unwavering support, Amazon could afford to sell books for what it paid for them — something no physical bookseller could do."
While the willingness of investors to pay large amounts of money for the stock of a company that makes little or no profit has been important to Amazon's success, it is also worth noting that through most of its existence it has been exempt from the requirement that it collect sales tax, unlike its traditional competitors. This has allowed it to undercut them in the market giving the company an enormous competitive advantage courtesy of the taxpayers. The savings from not having to collect sales taxes dwarf Amazon's cumulative profits since it came into existence.
Having read through the comments here, I will make a couple of quick points.
1) Don't waste anyone's time or kill any electrons talking about customers being obligated to pay the tax. This is a blog about the real world. No one sends their sales tax to the government for the things they bought on Amazon. What matters is the law as it's enforced, and that means that Amazon's brick and mortar competitors (which includes many Internet sellers) had to collect state sales tax all along. Amazon has just recently started collecting taxes in some states.
2) Not having to collect sales tax is a huge subsidy to Amazon. (Yes, it is a subsidy. States and cities collect revenue -- if Bezos gets out of paying it, then everyone else pays more. It is the same thing as if the governments sent Jeff Bezos a big fat welfare check every year.) And it mattered a huge amount to Amazon's growth and survival. If it thought it could have raised prices by 4-8 percent (the amount of state sales tax) without hitting its market share, it would have done so. The fact that the company has generally operated with near zero profits indicates that collecting sales tax would have been a very big hit.
Note: Typos corrected.