A new car leaves somewhere traveling at 60 mph. 

The rear differential locks up. The car crashes and burns with everyone trapped inside.

 Now, should we initiate a recall? 

Take the number of vehicles in the field, A, 

multiply by the probable rate of failure, B, 

multiply by the average out-of-court settlement, C. 

A times B times C equals X. 

If X is less than the cost of a recall, we don't do one