No matter how generous those book advances seemed, the publishers simply could not compete with his per - book royalty figures. (ingramspark.com)
A figure is not given for gas royalties, but the total royalty figure from ALL sources other than coal (minerals and gas) was $ 106 million in that year, so banning new gas wells is unlikely to reduce future royalty revenue by much. (cedamia.org)
The same could be said for Barnes and Noble / Nook, Kobo, etc., with slightly different royalty figures. (sciencefictionfantasybooks.net)