The Nexus 5 in both 16GB and 32GB variants is on sale today through eBay’s daily deals. The 16GB model in black can be had for as little as $334.99, which is $15 cheaper than you would pay through Google Play. You also get free standard shipping, which would run you $9.99 if ordered from Google directly. The 32GB model in black, white, or red is available for $374.99, which is also $15 cheaper than you would find on Google Play. The same free shipping deal applies.
I know that the Nexus 5 seems to be aging at this point, but for under $400, you won’t find many smartphones this good.