The authors have ingored the supply-demand curve to their own ends and pretended that the number of copies is a constant. Therefore each free distribution is lost income.

If we apply the same logic but state that consumers' disposable money is constant; then they are overcharging by £130 billion, as this is the money being made by them that they should be earning by distributing these copies themselves (at a lower cost per consumer).

Since copyrights are government sponsored monopolies it appears that the copyright owners are guilty by their own admission of monopoly abuse and should be punished.

It's only logical.