A big difference in price is 4G or 3G. The difference is the speed of the data. If you are not in a 4G area then it's not much good to have a 4G phone as you can't use it. Take a look at the coverage map to see what's available for you.
For the most part Android phones all work more or less the same. The variables are the size of the screen, speed of the processor, and amount of built in memory. You should be able to get a 3G lower end android phone for $0. The more you want, the more it will cost. A higher end 4G phone will be $200. I have a low end 3G android phone and I think that it's great. The thing that I want the most is a larger screen.
One thing you should know. The battery will not last as long as an older talk only phone. With everything turned off I get about 90 hours of stantby max. If I use it it's less. If I do a lot I have to charge it every day. I could go a week easy on my older phone.