theodp writes "Borders said Thursday that it was severing ties with Amazon and will compete directly against the e-tailer with its own website. The loss of Borders could cost Amazon $80-$160 million in annual revenue, according to one estimate. 'Amazon could gain market share in book selling over time because it will have an advantage over Borders, which now will charge a sales tax for all books sold. Companies have to charge a sales tax for Internet sales if they have a physical presence in states that collect sales taxes, [Stifel, Nicolaus & Co analyst Scott] Devitt said. Amazon collects sales taxes only on books sold in Washington, North Dakota, Kentucky and Kansas. Borders would collect sales taxes in all 50 states, the company said."