If you're paying for yourself and either buying used or slightly outdated hardware(or getting a new Nexus 4), this is probably completely true. If you're bundling several smartphones and regular phones, the contract price can win out. You still need to shop around to see what the best price is if you're going with iOS or the more expensive Android devices.

For example, since I'm sharing a plan with my family, the ATT contract comes out to around 20% cheaper than a similar contractless byo device Virgin Mobile service for iPhones, upgrading only after the contract is up.