For an unlocked iPhone, how much?

I'm thinking of getting an unlocked iPhone then hooking it up to a network? I know it's expensive (initially) but eventually won't it pay for itself? Or honestly, is a "plan" so much better? I mean you could purchase packets of data (if you need it) or just remain on Wi-Fi only, right?

Don't get a sprint one FYI

Not that expensive on contract, iphone 6 is $199 on contract, iphone 5C is free on contract.

I always buy iPhones fully unlocked from the Apple Store. You have to pay more up front because the cost of the phone is not subsidized by your carrier, but in the long run it costs the same, and you're not tied to any specific carrier or plan.