Fined $27 million. Made $64 billion in the last 3 months. So that's about 1 hour of profit. I'm sure they've been taught a lesson they'll never forget. EDIT: as pointed out below, that was revenue not profit. But apple make so much damn profit it's not as crazy different as it would be for most companies. So it's more like 2.5 hours.
Classic mistake of conflating revenue with profit. They made closer to $25 billion. Ignoring that, it's a mistake to think that these "small" amounts don't matter to companies. They just lost the yearly salaries of 150 or more engineers. It's worth it for them to assign 5 guys to add and maintain a feature that notifies customers of the performance drop.
You're view is right if the only reason they didn't inform people was the engineering demand. I personally don't think that was the only cause.