you may be thinking about this study: https://en.wikipedia.org/wiki/Public_Finance_Balance_of_Smoking_in_the_Czech_Republic

there is also famous ford pinto scandal, where ford pinto would sometime catch fire during relatively small rear-end collisions, ford knew about the problem, the change in design would cost $15.30 per car, yet ford decided it is cheaper to let few people die and deal with the consequences.

https://en.wikipedia.org/wiki/Grimshaw_v._Ford_Motor_Co.