Chapter 4 - Inverse, Exponential, and Logarithmic Functions - 4.1 Inverse Functions - 4.1 Exercises - Page 418: 89

$f^{-1}(1000)$ represents the amount of dollars used/spent to build 1000 cars.

$f(x)$ represents the number of cars that can be built for $x$ dollars. This means that the inverse function represents the amount of dollars used/spent to build a certain number of cars. Thus, $f^{-1}(1000)$ represents the amount of dollars used/spent to build 1000 cars.