Actually did a search. Nissan appears to have accepted responsibility for the defective CVT for your car (2003-2010). The warranty was actually doubled to 10 yrs and 120,000 miles.
Furthermore, on that site it states:
If my vehicle is outside of the extended warranty, how will you address any service issues with my CVT?
A. Most vehicles equipped with a CVT that are out of warranty will now be brought back into warranty with the new 10 year/120,000 mile coverage. In the unlikely event you need a repair beyond the extended warranty period, Nissan is working to change the repair process and reduce the cost of repairs. Also, the MSRP of a replacement CVT has already been reduced. "
So given the above, I'd contact Nissan and ask about question #17" and clarify if the dealer charging you $6,000 is the "changed repair process and reduced cost of repairs and if it includes the MSRP reduced price?
But I will say as someone else has mentioned it, while some cars can/do make it to 200,000 or even 300,000 miles, it seems generally a bit unrealistic to expect every transmission to make it to 200,000+ miles no matter what make/brand. I think when Nissan extended the warranty for their CVT on those cars, that was basically done to help bring back faith for consumers in their brand. If they are so certain about their current transmission quality, then it seems a bit odd that they wouldn't up warranty on the transmissions of all their new cars to 10 yrs/120,000 miles.
I know someone who's Murano's transmission went out at around 100K, but that person got rid of the car. Probably was before the extended warranty was put in place. I'm sure he'll be pleased to hear that he could have kept the car and had Nissan replace his transmission for free.