Graphic Discovery, Howard Wainer: [E]ven the magic of logarithms does not always tame profound differences. One example of this appeared on July 8, 1997, in the automobile section of the New York Times. It listed the names and prices of the forty-seven convertible car models then available. They ranged from the $15,475 Honda del Sol all the way up to the Ferrari F50, priced at a cool $487,000. The range of prices was so broad that the illustrator of the Times could not fit all of them on the same graph and so had to resort to merely listing the most expensive ones separately. "Aha," I thought, "you should've tried logs!" Then I did, figuring that they would linearize the plot. They did, but not all cars fell on the same straight line (see figure 1). The thirty-four least expensive cars fell on one straight line, then there appeared to be a jump for the next seven cars, then another jump for three exotic European cars, and then on another line with a much steeper slope were the three most expensive cars.
Thus we have discovered that the cars at the upper reaches of the domain have prices that exceed what a single exponential increase would dictate. Would some other way of thinking about convertible prices provide a clear functional relationship between rank order and price?

Taking the next step (inverses) in this ladder of transformations does the trick [One approach when data are skewed is to transform them to symmetry. For mild skewness, a square root often works; when it is more extreme, a logarithm; when more extreme still, an inverse. These steps in progression are often called "Tukey's ladder of transformations."] If we make a plot showing how many of each car we could buy for one million dollars (about sixty-five Honda del Sols but only two Ferrari F50s), a simple linear relationship emerges (see figure 2). By making this transformation, we not only gain a linear relationship between rank and a function of price, but we also have a metric that is easier to think about and to comunicate to others. We also discover that two other groups of cars separate themselves from the pack: "nice convertibles" and "really nice convertibles".

Source: Graphic Discovery: A Trout in the Milk and Other Visual Adventures by Howard Wainer

related items:
Notes on the use of data transformations, Osborne, Jason (2002), Practical Assessment, Research & Evaluation, 8(6)