Forgot to mention that the business I own pays for my phone usage, whereas my family pays for the wife and son's phone. So Amazon receives two payments each month. Under the plan whereby I keep unlimited data and my wife and son upgrade phones and each buy 2 GB data plans, my business' monthly share of the bill does not change, BUT the wife/son portion increases $60 a month. If we share 4GB a month my portion actually goes down about $3, whereas their portion goes up about $53.
It's inevitable--unlimited data plans will be totally eliminated in the future and shared data plans will be standard. As more people get smartphones the cost per GB will come down. I might just cave in now and get shared plan.