I don't know about it being low effort to be compliant. We spent most of a year with a significant portion of our software engineering teams devoting time to GDPR even though we are not any kind of data collection company. It's the legal requirements -- we had to audit every last piece of software, make little tweaks if necessary, etc, just to ensure we were demonstrably compliant with the law.
I wouldn't be surprised if 150B is actually a low estimate.