You said there was no "other loss caused by the breach." Why wasn't the cost of rebuilding the engine an other loss caused by the breach? After all, if the contract had been performed, he wouldn't have had this wasted effort.

Good point. Let me try the question again.

It wasn't wasted effort. If Enthusiast had performed the contract, Mechanic would have been paid $8,000 for his work. In our damage calculations, we've already included the $8,000 as something we're going to award Mechanic, so he's going to get that as payment for his work.