Dream/Wish/Technical question: EF 500mm f/5.6 L IS or 600mm f/5.6 L IS

[qwRad]

Hello everyone!

I'm not sure if this has been discussed previously and I couldn't find anything definite (only a few mentions) with search so here is my question/wish/dream.

Why isn't there a high quality 500mm or even 600mm f/5.6 (or maybe f/6.3) lens in Canon's lineup that would be closer to "acceptable" price levels vs. the new (and old) f/4 lenses in the same range? Is there some technical/physical reason that it wouldn't be significantly cheaper to produce or is it just a marketing/strategy decision. I think that there would be high demand for such a lens at maybe 3000-4000€ or preferably even less of course.

Thanks for your responses in advance.

EDIT: And shouldn't there be quite a significant weight saving also for such a lens compared to the f/4 variants?