Building a Device Lab (2015)
buildingadevicelab.com
buildingadevicelab.com
Assuming you have an 1800W circuit (pretty standard) that's almost 400 phones. Even if you're in a Victorian-era home with ancient wiring and a 1000W circuit you can run two hundred phones off of that.
Also, having been to a bunch of device labs (and having my own mini one in my apartment with 15-20ish devices) bandwidth is never a problem. You typically only use one at a time, or with a shared lab maybe three or four at once.
The most effective "device lab" is a box of Androids and a few of the latest iPhones, with some chargers and a nice powerbank. You can just take the phones back to your desk and use them there.
I also have never met anyone who uses phones as "servers". In my experience you grab a phone, test something, and put it back, no? Maybe if you're before a big deploy you test on everything you've got.
I'm also not talking out of my ass here - I've made the CSS framework that's compatible with the most devices by far (including IE5.5 and certain versions of the Nintendo DS browser.) Testing it requires a tremendous number of physical and emulated devices. If you want to take a look, it's at http://mincss.com
The titled intrigued me and I thought it'd have much more information on things like automating test builds and using unique device/OS features, not how a company worth almost billions can save a few hundred dollars by ignoring 20% of its users.