[ConcernedCitizen]

In terms of scale and real world consequences, the Colonial Pipeline breach was probably the "biggest".

They shut down 5500+ miles of pipeline and paid a $5 million ransom in the end. $2.3 million was later recovered.

Yes, the largest amount they paid was included in the cost of oil they couldn't send through the pipes. I can bet that alone was in the tens of millions. Not the actual security response they paid for man-hours and on site operations for remediation.