By the power of truth, I, while living, have conquered the universe.
Such idiocy...
CEA is not just enhanced graphics. It has new skulls, new Terminals, new easter eggs, XBL co-op, 7 new maps and other things Frankie says they'll reveal later. I've noticed a pattern since the game was announced - the people who aren't excited about this game are the ones who jumped on the bandwagon in Halo 3 and never experienced the original, nor were they able to appreciate what it meant for FPS games.
Plus, even Microsoft was generous with the price by making it £30/$40. That's well justified if you consider a map pack of 3 maps is roughly £10, since CEA comes with 7 new maps that's about £20 already justified. Then there's the campaign with all new features which is certainly worth £20 by itself, so whilst the game could have been priced at the ordinary retail amount they chose to make it £10 cheaper.