However, ebooks are less functional than physical books in some key ways, at least with current DRM - you can't easily lend a book (the restricted amazon form is pretty weak), and you can't resell it. Assuming "like having a nice physical object" and "convenience of carrying all my books on one device" are a wash, the lack of lending or resale should definitely make the ebook cheaper.
However, ebooks are less functional than physical books in some key ways, at least with current DRM - you can't easily lend a book (the restricted amazon form is pretty weak), and you can't resell it. Assuming "like having a nice physical object" and "convenience of carrying all my books on one device" are a wash, the lack of lending or resale should definitely make the ebook cheaper.