Selenium IDE saved us hundreds or thousands of hours.
For example, my team took an existing web app with no tests, and had the project manager and junior business analysis go through the entire app with the Selenium IDE, writing tests.
This enabled our dev team to start coding fast, and refactoring fast.
In parallel our QA team then took those tests and used them as first-drafts to create even better tests that were generic, maintainable, randomizable, and so forth.