The Finnish phone maker is now offering the smartphone at $49.99 on the AT&T network, down from $99.99.
Microsoft unveiled its next-generation mobile operating system last month, and confirmed that it will not be compatible with any existing handsets when it lands later this year.
Nokia, which is expected to roll out a new range of compatible handsets, has defended the move to reduce the price of its flagship phone.
"This move is a normal strategy that is put in place during the life-cycle of most phones," Nokia spokesman Doug Dawson told The Wall Street Journal. "It allows a broader consumer base to buy this flagship device at a more accessible price."
Nokia is yet to confirm whether the Lumia 900 will receive a price drop in the UK.
