google play doesn't regularly discount phones/devices (as much/frequently as a retailer like Best Buy)
That saying, the most recent price drops:
Last time, Nexus 4 dropped by $100 in august 2013
7 days ago, the GPE Xperia Z Ultra dropped $230 to $450.
Hence, Nexus 5 will typically be $350/$400 for 16GB/32GB..... will other phones be cheaper (LG G2, HTC One 2013)?
do you want those phones?