When shooting wildlife, you'd normally carry a long supertele for the long-distance shots (often with the expectation of having to crop a bit as well), as well as a shorter zoom for larger animals or things which come closer. You'd probably use them at around the same frequency.
This lens fits the 'shorter zoom' function really well, but the 500L works better for the long-distance shots.
At the moment, you're pretty much stuck with the 100-400L, which really isn't adequate on a dedicated wildlife shoot if 50% of your shots are coming from it...
If someone is really serious about this type of photography, wouldn't they be more likley to want a 600mm/4 if this new lens is good for 560mm/5.6 (we won't know for a while). I just don't think someone with a 500mm/4 would bother buying this lens at all or vice versa.
I'd expect Canon is similar to any other hard goods manufacturer when it comes to product costing and pricing. So many factors in play and they likely have a well honed process to establish MRSP for launch. Manufacturing cost likely doesn't have much, if any part as you mention; pricing versus competitor and what market will bear are others. They'll also consider where this lens fits within the current & future Canon lens lineup, which lenses it might displace for sales, who their target market it, how many units they expect to sell projected over time, lost projected sales of other lenses in the lineup, and the variables go on.




