An f40 is a slow lens but a fast car

That lens is really expensive. The 1200mm f/5.6 has a 214mm aperture. TEC makes telescopes with similar sized fluorite glass, with supposedly very high quality optics. A 1600mm f/8 (200mm aperture) is about $28K. A 2500mm f/10 (250mm aperture) is about 56k, which seems a bargain when compared to the canon. No autofocus or electronics, but you're paying for the glass, right? Sure the canon is faster, but is that really what you're paying for?

Maybe it's just that there aren't that many, and it's a supply/demand thing.