2011's MSRP at 85K they sale for 80-81K on average
a 2010 with the same miles as yours would be maybe 70-72K private party
that 09 you have is really low mileage and would sell for about 66Kish to the right person... thats why im only asking aroud 63K for mine as it has more miles
thats where the market is on these... i know
here is an excel sheet with some research i did while preparing to buy a 2012.... it shows ballpark auction/dealer trade in and private party for a 2009 GT-R with 10-15K miles... so yours would be more in the higher range of mid 60's
hope this gives you some perspective
also take a look here to see what most are selling and buying for
http://www.nagtroc.org/forums/index.php?showforum=101