I'm hoping that you are mistaken for those that share apps with their family. A single $10 purchase versus a $10 in-app purchase per device. So far it hasn't been definitively clear as to which way it will go, so below is simply the information that I had come across prior to this thread. We have a little less than a week to see which way Nintendo will go.
I had originally heard about the two different applications through Outside Xbox's alternate channel
Outside Xtra on YouTube, but
PCMag.com seems to be reporting the same thing.
"Refreshingly, Super Mario Run has no in-app purchases. There's a demo consisting of three levels available for free, and the full, paid-for game priced at $9.99. However, there's one additional barrier to play beyond the price. Nintendo decided to only allow the game to be played if an active Internet connection is maintained. If you happen to travel somewhere your iPhone or iPad loses its signal, Super Mario Run can't be played." (the source article is hyperlinked up above)
I'm not overly excited for the excessive requirement for constant online connection, but I'm hopeful Nintendo will back off of their requirement and just notify the user that certain functions are unusable when offline.