I used to visit the music education company TrueFire in St. Petersburg, Florida annually when my mother was still alive. She lived about 25 miles away. TF people are very nice, and I went out to dinner with them on at least one occasion, as well as eating community-style lunch on-site.
I asked the about certain courses, like one on harp guitar. I asked how many people actually own them. Some find antiques, and some need to have one built.
They replied that it wasn't important how many course copies they sell. It's about creating the content for things they feel are important to document.
On that trip I left a camera battery & charger plugged in, contacted them to see if I had left it, and they located it. They shipped it back to me, with an autographed copy of a CD, because someone at the table overheard my incredulous view of the harp-guitar.
I initially thought the CD was a joke, until I listened to it! It's not like the heyday of harp-guitars, but it's skillfully done and listenable. I loaned it to someone and his son borrowed it. I didn't get it back for years, but it was eventually returned!
Murray