Harder when it’s primarily a web app, but customers can be convinced to try mobile/desktop apps at times. Maybe give a discount?
Downloading and configuring CouchDB on their PC isn't something I can do for them, but it's really simple and easy to do and I provided step by step instructions.
I didn't charge them anything at all to get and use the offline first version of the app. They already paid for the online version (that's a yearly subscription fee) so there was no extra charge at all.
They really were not at all concerned about a long term outage. I can understand that because widespread outages have been pretty rare, and the app has never been down for any significant amount of time for 20 years now. So I think it was really a lack of urgency.
Innosetup is still a thing, and there are alternatives. Installers can take parameters, or be built on the fly. That's what we did at one place to install postgres and other apps for a customer, while making it as simple as possible. Next, next, finish.
Discount refers to reducing the cost if they went thru with it, lack of an extra charge while nice is not an incentive in itself.