1 and 3 are the most effective. Option 2 is useful until there is any real demand for your data, and then you're back to trying to prevent automated scraping by your paying customers.
If you are charging someone for access, then presumably you are requiring them to log in to access the data. In that case, it should be pretty straightforward to throttle or completely block them if they are doing something (e.g., scraping) that violates your terms of service. Then you charge them again to use your API.
