I worked on a local first version of an app I sell. I use CouchDB to store user data so it was pretty easy to implement because CouchDB will sync a local CouchDB to the Cloud based CouchDB as soon as any changes are made. That app is now 20 years old and over those years I've had users who quit using it call me years later to ask if I could give them access to their expired account or a copy of all their data. CouchD…
Harder when it’s primarily a web app, but customers can be convinced to try mobile/desktop apps at times. Maybe give a discount?