how is 'instant market value' derived?
From Cargurus Home......Instant Market Value is the estimated fair retail price for a vehicle based on similar listings in the market. We analyze millions of currently listed and recently sold cars to determine the Instant Market Value for a vehicle based on year, vehicle condition, trim, mileage, transmission, options, region and other factors.
They just guess. How do I know? I see a Prius V they say is $500 over market but truecar says the same exact car is $2000 under market. Each website says they use the same pricing methodology.
Yes but each website uses different sales data. Prices also vary from area to area.
I do suspect that all these sites use the asking price, not the actual selling price so negotiate the price down.
Both say they're using actual sales data (the "asking price" would be useless) so they're using the same exact data. Once you normalize the options the only two pricing variables would be year and mileage (which are probably 90% of the selling price determination). Note, they would not know if the car was a smoker. So, a variance between the two sites of $2500 makes these sites totally useless.