Not quite sure why Modern Elmo was given such short shrift (although, off-topic, the bad teeth cliche has always puzzled me - with the NHS I'd suggest that, in particular, our poor generally have better teeth than America's poor)
Fundamentally, his question is sound, it just needs expanding - why are we buying JSF, instead of buying something that's not as cutting-edge, but is a lot more affordable?
If we're not careful, we'll end up ploughing a lot of money into the programme, see cost keep increasing and platform numbers keep decreasing, before finally having a future government that will announce that we can't afford it and so will cancel it.
MRA4 all over again.