I think what they are saying is there is no way to compare a good when it's free to when there is even a nominal cost.
My "counter evidence" to your example could be something like: I bought House on DVD 10 years ago because my friend who had pirated it told me it was a good show to checkout.
My "counter evidence" to your example could be something like: I bought House on DVD 10 years ago because my friend who had pirated it told me it was a good show to checkout.