Sounds like you need to make things easier rather than harder. They have a clear economic incentive to scrape your site and will continue to do so. Rather than spending your employees time on it, open it up as an API. If someone starts hitting it too hard, send them an email to back off.

If your only competitive advantage is your pricing, then you're in a losing game. Otherwise, you're probably better off spending your efforts on making your product/service better.