I just bought a $69 Nokia Lumia 521 (Windows Phone) off contract. Mozilla isn't at the forefront here - both Nokia/Microsoft and Motorola are driving down the off-contract price point.
These phones are actually pretty damned decent for the money!
I'm looking to equip everyone in our startup with a 'company' phone, that is to say one that I can wipe remotely without anyone being upset.
Once 8.1 is out, the 521 will allow me to put a secure VPN connection, easily toggleable, has a good enough for hell RDP client running some powershell.
I can also fairly easily make something to use WMI to query a bunch of important details for our prod environments.
That's really not a bad price point for such a device.