Huge miscalculation on AMZN's part because as they are now guaranteed to owe at least the $269M tax bill to TX as well as opened themselves up to other penalties in TX as well as other states. You don't mess with Texas.
Their financial statements will have to be restated.
This news alone should the stock down 10%. They would have write down the cost, still owe back taxes and spend money to setup in another state which most likely will also collect sales tax in future. Are they going to close all the locations? If they can compete with collecting sales tax why take such action? why not just collect the sales tax?