There are multiple models:

1. Like Sentry - open source all the features, provide the cloud (hosted) version. Most businesses don't want to self-host, but want a bit cheaper alternative

2. Paid tier, buy once - own forever with 1 year update support. Later you can charge lower price to extend the update cycle.

3. Blender model - donations. Very hard to get it right.

4. Laravel/Next.js model - Open source the tooling, monetize the platform