Comment by _ixdf

I've written a book that I sell as a physical copy and an ebook. I don't advertise this, but when they buy the physical copy they get sent the ebook for free with this message:

  "You bought my book, and because of your support, I am able to make a living as an artist. It means a lot. PS. if you want to read the ebook, it is included in your purchase of a physical copy. Press "View content" to download. However, I recommend waiting for the real deal."

The reason I do this is because in my mind, they have paid for the content not the paper it's printed on, so the ebook is a part of the same purchase and is an extra convenience for someone who might want to read on their Kindle or phone. It's also a way to reward customers with extras, leaving them happier and more likely to leave a positive review. They also get all future revisions and editions emailed to them.