What makes some cell phones worth ten times others?

I have Boost Mobile (Sprint) and a Kyocera Android phone (35 bucks)with a 30 dollar per month charge, unlimited text, unlimited calls and 4 gigs of data and I'm pretty happy. The Kyocera is IP54 rated so you can get it underwater (for 30 minutes), no issue. Getting an ordinary phone wet is usually the end.

being a senior citizen, I don't need (or want) the latest and greatest, heck, I cannot even figure out half what this phone will do....lol