Agree with Jimi that one of the most proper antonym for "free of cost" is "available." But, "purchased" or "priced" could work as the opposite of "free of cost." This e-book is free of demand. This guide is priced. That dessert was free of demand. That dessert was purchased. G. https://zanekjfea.blogoscience.com/43126081/detailed-notes-on-hairy-pussy