I’m just about to publish a book. There is a concept called “Library price” where you can make up your book when a Library purchases it. So let’s say I sell my book for 9.99 on iBooks but I can charge 20.99 to sell to a library. The issue is that the library may only buy one copy. Your best bet and the best way to support the author is still to buy the digital book as printed books have a cost associated with them (printing, binding, etc) and the margins are much lower. Hope this helps.