Hi Tidsy!
Sorry to hear about your son, hope he gets well (and back on the sadle) soon!
Loth, Yes you're right!
They're terribly expensive, not only Trek, but I guess every bike brand.
I have no idea how much they profit on each high-end bike they sell, but I guess it is a lot...
Nonetheless, I guess some components can be very hard to develop, because they have to be as light as possible, and still be extremely resistant and precise while under really bad conditions.
Like deraileurs for example, they have to maintain funcionality while getting beat up by rocks, drowned in mud and water, and still run for miles and miles until you get back home. Frames also need to be as light and tough as possible, breaks have to be potent but still light...
I guess it isn't easy and it doesn't come cheap, but it is still a lot to pay for something that can't carry you home unless you pedal...

I wouldn't give that kind of money for a bike unless I was a professional rider, or for a camera unless I was a pro photographer, so what I do is keep an eye on the ad section of the forums and wait for a good deal. That's how I bought my camera, all my lenses and this frame. Still expensive, but doesn't hurt as much.