You can probably use the iPad's builtin hdmi out feature for free, but it will output an iPad-shaped display. The one you pay for will dynamically resize to fit

You can probably use the iPad's builtin hdmi out feature for free, but it will output an iPad-shaped display. The one you pay for will dynamically resize to fit the screen it's attached to and display different stuff. Not a huge difference but it isn't like they did NOTHING for the feature.