"If they had designed the pit well in the first place they...

"If they had designed the pit well in the first place they wouldn't need to be coughing up more dough to modify it now."

That's patently rediculous. Pit Designs are based on geological data collected from drilling. You are essentially using a grid of coke can diameter holes spread over the resources to infer what the ore body looks like. You can't know the ground with 100% certainty. It's not like designing a building with materials that have 100% known properties.

It has to be expected that the pit design will change as the resource is exploited.