Few days ago Microsoft Store offered such a deal on Lumia 950, and this time the offer is available for Lumia 550 too. You can now buy Lumia 550 Unlocked from Microsoft Store at 50% discounted price, i.e. $69.00 (was $139.00). This deal is only valid for US customers with free shipping and free returns.
Right now (12/26) the phone is out of stock, and since the offer is only valid for limited stock, you might have to wait for sometime for device to be back in stock.
Buy one for yourself or gift one to your loved ones : Lumia 550 Unlocked from Microsoft Store.