This trend can be used to benchmark a car model vs its competitors within the same price range. There will always be outliers, but in general this trend works as a benchmark. As an example, if the MSRP of a car is 15 K and it sells 1,000 cars that is a failure. If it sells 500,000 cars, the car would be is a resounding success.
There are always qualifiers which have to be taken into consideration, these are either limited production, supply constrained, some other economic mechanism, or new model year/change in style mechanism at play.