Not my experience with open source at all. I get very few bugs and PRs about actual defects. By and large they are feature requests that are very important to the submitter but not necessarily to me or other users of the project. And they do not care about quality at all - they only care about solving their own problem as expediently as possible and don't care if they introduce new bugs, break compatibility with existing users, or reduce maintainability of the code.

As for paid vs unpaid work - I care about quality in both cases. But I'm much more motivated to care about someone else's use case if I'm being paid.