It's free to use and download with an optional Pro subscription that includes additional features and makes > $500/month.
Key things that have helped the revenue in 2021:
- Released a major new version 3.0 which blocks all YouTube ads and has kicked along sales and improved the conversion rate considerably
- Apple's small business program began this year that only takes a 15% cut instead of 30%
- After a long time developing and updating the app, it now includes most features requested by users, so it's achieved a 4+ star rating on the App Stores
- Downloads were originally weighted heavily towards the macOS version but it is now getting more usage on iOS which is growing the overall sales volume