"differentiation can be seen by customers as a distance, as a lack of closeness to substitutes.
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A more quantifiable way is to see it as the reciprocal of price sensitivity
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The more differentiated an offering is, the less its sales will depend on customers’ price comparisons.
A highly differentiated offering may appeal to a comparatively narrow group of customers, but those customers will see no close substitute, and will not choose a substitute because it has a slightly or moderately lower price. The price difference would have to be commensurately high to affect their choice.
Price sensitivity measures how sensitive the sales volume of an offering is to marginal changes in price differentials between that offering and its substitutes. It therefore indirectly measures the price consciousness of the customers.
In a limiting case, the degree of differentiation is zero or infinite. Where it is zero, the offerings are homogeneous and the slightest price difference would shift customer choices. Where it is infinite, ... the offerings are not substitutes at all and no price difference would shift choices.
The phenomenon of the discounter illustrates the usefulness of treating differentiation as the reciprocal of price competition."
Trechos retirados de "Creating Value Successful business strategies" de Shiv S. Mathur e Alfred Kenyon.