After initially launching in L.A., Phoenix, San Francisco, and Seattle, Amazon is now expanding its same-day delivery program to six more cities, New York City included. For an additional charge of $5.99, Amazon Prime customers can opt to have their new purchases delivered to them before the end of day, provided the orders are made before noon. If it succeeds in the long-term, the digital retail giant is set to eliminate one of the few advantages physical retail stores still have over Amazon.