The depreciation is higher for the Nismo only initially as its more expensive to buy. Once the car is over 1 year old with at least 6000+ miles its priced in the high 20,000s some brazenly priced at £30,000. Once the car reaches 2 years the Nismo tends to slow in depreciation compared to the equivalent GT.
In UK the only Nismo 370 I have seen below £20,000 was a 2015 with 72,000 miles priced at £18,000. Which literally was for sale for 6 months.
Initial depreciation is steep on the Nismo. Once at the lower 20,000s usually a 3 -4 year old car depreciation is already slowing down for the Nismo.
According to carsalesbase site, Nissan are still selling over 200 cars worldwide per month. Some dealerships are discounting up to £4000 pounds to boost sales.
The standard car rate of depreciation is slower initially compared to the Nismo. I still think the Nismo will hold more value in future. A 10 year old Nismo is more likely to command more than the GT equivalent same year same mileage