Why doesn't Sigma or Tamron.......

Why don't the big 2 aftermarket lens companies make a straight 500 5.6 or 600 5.6 and price it at or just below $2k?

It seems with their ability to make zooms that reach out to 600mm and price them at the $1k mark, they should be able to make a 500 or 600 5.6 prime that would be sharp, not too heavy and reasonably priced.
I know their zooms are 6.3 on the long end but I would think the 1/3 stop down to 5.6 would be doable with a prime.

It would really help us budget bird/wildlife shooters.

Discuss.

They go where the most demand is. So they stick to zooms and higher volume primes. You are correct they could undercut canon and steal market share, but the volume would be low enough that R&D costs are better spent elsewhere.

I sort of wish they had come out with a new 150-500 'Sport' for $2K instead of the 150-600 sport, in the sense that the range would be a bit sharper and lighter. Nevertheless I do much look forward to the reviews...

It will either be that sport Sigma or the fabled EF100-400L IS II for me in 2015...

Canon better pull up its socks and deliver what prosumers want because Sigma & Tamron are "doing it" and for less...

There is always the Sigma 500 F4.5, I tried one on a 1D4 and thought it was pretty nice.
True it is dearer than an F5.6 would be but not too silly second hand.

All great responses.

I saw the 500 4.5 but with a TC it would likely not AF the 7d mk1.
Maybe with some tricks.

I look forward to the new SIgma Lenses. Tamron has done VERY well with theirs and so I think SIGMA will do even better.

SUpposedly the new 100-400L is OUT in testers hands being field tested. I guess we'll see when/IF it comes out how it stacks up to the others.