Just for fun I also did a cost comparison with the Chunnel, and...

Just for fun I also did a cost comparison with the Chunnel, and guess what? Using two methods for estimating the change in purchasing power of the pound, and the current exchange rate, I came up with figures of ~$412 million per km (retail price index), and ~$590 million per km (average earnings). So by either measure, Airport Link, at over $700 million per km, is more expensive per km than the Chunnel!

Holy cow, Batman!