That is low mileage for a worn out clutch, unless it has been abused.
Is the car on its original clutch or has an aftermarket been fitted?
If original then I would guess that it needs a new clutch and fly.
If biting that high, then it must be slipping badly????
New clutch and fly kits are in stock at half the price that you have been quoted, however, use the expensive Nissan prices for your negotiations.
I am assuming that your car is the HR model, please clarify.
Just drop me a PM if I can help you further.
Alex.