Nokia 635, $40: http://www.amazon.com/AT-Nokia-Lumia-635-Contract/dp/B00LBFF...
We bought one for my future mother-in-law, because the Windows Phone tile system was easier for her to deal with than the Android home screen. Plus, when she dropped it in a puddle after a few months, no big deal.
I don't understand why these low cost Nokia's get so little love here in the U.S. My 520 was $50 a few years ago and is a rock solid piece of hardware. I guess it's the missing apps on Windows mobile?
It's great. I love it. It's not quite as nice as my old phone, but it's 90% of the value, for 15% of the price.
And in some ways, it's better than my old phone (lighter, more damage resistant, better battery life, better cellular reception)
EDIT: Except it comes in 512mb and elusive 1gb RAM versions, with identical product names and prices, so I have to search around to get the good one. This is how it starts! Perhaps I don't need a smartphone...