The scientists developed a survey to put a dollar value on the natural resources damaged by the BP Deepwater spill by determining household willingness to pay for measures that would prevent similar damages should a spill of the same magnitude happen in the future. Survey information included descriptions of damaged beaches, marshes, animals, fish, and coral.
On top of estimating the impact of the spill, the $17.2 billion represents the benefits to the public to protect against damages that could result from a future oil spill in the Gulf of a similar magnitude.
So their estimate of the cost of the spill is based on:
- How much survey respondents claim they might be willing to spend to save the cute animals, and keep their vacation spots pretty;
- Estimates of the cost of a program to prevent it from happening in the future.
That is now how you calculate costs!
We may still learn that this event was a civilization-ender.
And don't forget, nobody will ever do any prison time. The fact that the BP "Corporate Person" has not been executed for this is a crime against literal Humanity.