Suppose a TV was manufactured 5 years ago in 2013, and it had a market value of 50,000. However, demand for TVs was very low and so it was left unsold.
Now, in 2018, it is sold for a market price of 80,000. What amount is added to the GDP of the economy in 2018 with respect to this single TV?
The market price of the TV in 2013 was added to that year's GDP. So, there is a difference of 30,000 between the old price and the current year's price. So this value of 30,000 is added to 2018's GDP.