It is a fair price because they retail for $700+ with the current exchange rate, and its an oil/air separator, not a catch can, I think there's a difference but cant remember what it is... and nismo items are extremely well made too. good luck with the sale anyway mate, hope that helps.
*edit*
found an article that explains the difference between the two on autospeed.
"a catch can receives blow-by oil and allows fumes to vent to atmosphere after being filtered. On the other hand, an oil-air separator internally filters the blow-by oil and allows only clean air to enter the car's induction system. This is the favoured approach from an emissions and legality perspective, but it doesn't look as siik when you pop the bonnet."
hope that helps