More about the 5 Best Frontend Error Monitoring Tools.
Rollbar is positioning as an Enterprise APM service with observability tools and a high price tag. Sentry is more developer-focused with functionality to correlate frontend and backend data. For a cheaper, front-end only alternative, consider TrackJS.
With TrackJS, the focus is on errors occurring on the browser. Filtering is second to none, and the quick views of trending errors are helpful in digging past the 3rd party script noise. It filters down to the core issues.