Yeah, I guess that it is a bit expensive ( I got mine while on vacation in the states, so that made the price seem more reasonable). On the other hand, it's not like placing your computer on a pile of books to raise it to the right height - it allows for a lot more air circulation around the bottom of the computer, which has been quite noticable - my fan doesn't run as often or for as long as it did when my PB was sitting on my desk. Also it's transparent which allows it to sort of blend in with the rest of your desk.
Of course, if your desk is covered in wires like mine, that might not be so desirable...