So that's £35 quid of value provided by rivals?
If this functionality is truly worth £35, then that's £35 of extra value provided by every manufacturer who just puts the standard cable connecter on the device. Well, let's call it an even £50 because you can't lose it or leave it at home when you need it. (The other commenters above don't seem to have noticed that it's not even an HDMI cable, it's just an adaptor, you still need an actual HDMI cable to get a picture on your telly).
Either way it's a rip-off, do it this way though and you'll have starstruck bloggers claiming that Apple's magical supply-chain means they can't be beat on price or value and that feature list items like HDMI output don't matter to anyone but the spec obsessed.
(Unrelated rant: do you realise that to buy a 15 inch laptop from Apple starts at £1,500, while rivals start at about a fifth(!) of that. Yes, they're not as beefy in the spec department, but why link the screen size to the computing power so tightly? No wonder Apple fans are flocking to the iPad, their favourite manufacture has got a giant hole to fill at the low end of the market.)