For a marketing channel to be effective, it needs to offer the
potential to promote your book to an interested audience, at a cost which will offer a
reasonable return on your
investment.
Having an elevator in a tower, for example, has, by itself proven to have a
reasonable return on investment for several owners and OEMs, allowing for a safe, fast, and efficient way to eliminate the dreadful 80 - to 140 - meter climb several times a day plus a
potential bonus climb when something is forgotten up - or down - tower.