The majority of the market for a 800mm f5.6 isn't really going to be bothered about what it costs as long as it isn't outrageous. If the lens is better than the previous version they will upgrade to the new without a doubt. A few thousand dollar isn't here nor there for this end of the market and as a result canon will charge whatever the monkey throwing the darts comes up with.
I still think the price point is important. Of course some will buy it no matter what it costs, but those buyer numbers will surely differ - and possibly quite substantially - if it costs US$12,000, US$ 19,999 or US$ 25,000.