This thread may turn into a legendary one.
On a serious note now...
Bah! Only f/4? That's waaaay too slow. I'd pay $13k for a 600 f/1.4, but not for a 600 f/4....I don't think that a 600/1.4 lens is physically possible
Oh, it's no problem. Well, a bit of an engineering challenge, but that's all.
It's only when you get to a 600 f/1.2 that the gravitational field is enough to form a black hole -- and, even then, only with a gripped 5-series or a 1-series.
oops. Didn't get it in the first place