http://www.vgchartz.com/tools/hw_yoy.php?reg=USA&start_year=2014&end_year=2015&console=PS4
hmmmm.
Last year 2014, looks like PS4 did around 4.8 million units in the US.
Not sure how much a 50$ or 100$ price cut will increase sales but.... in 2015 the US sales should be higher than the 2014 sales of ~4.8million units.