Pure speculation, but the sales rate of the Nexus 5x and 6 could have been so low that there wasn't much inventory to dispose of when they stopped selling it.

Have you considered options like eBay or Amazon? Oftentimes the secondary market (even for a new phone) sees a dramatic drop on announcement of a new model, and you can still capture gains from that. [1]

[1] http://www.asymco.com/wp-content/uploads/2013/08/Screen-Shot...