Not sure. For comparison, I bought my 2010 LS in Jan with 27K miles for $13K. Low mileage is great, but as soon as you start driving it, it depreciate very rapidly. The other way to look at your deal is that's it's about $10K off of the original price, which compares to my deal (my LS new was about $24K). I would offer $16K and see where that goes, but you have to have the "I'm walking out the door" attitude!
Good luck!
Good luck!