The $100M model nobody wanted to build

Two weeks into the iron-ore haulage engagement, the client executive asked me for a summary. Three slides. Something he could take into the next capital allocation meeting. The full value-chain model — spare parts, maintenance cycles, haul routes, driver utilisation, fuel contracts — was going to take another month, and he had decisions to make in twelve days.

I nearly agreed. The summary version would have looked credible. It would have cited the parts of the business that were easy to read, and it would have quietly ignored the ones that weren't. The exec would have left the room with a number, and the number would have been wrong.

The reason models are boring is the same reason they matter

Business cases fail in the parts everyone skips over. In mining, that's almost always the haul. The haul is where the interactions compound — a 2% change in truck cycle time multiplies into maintenance schedules, driver shifts, port loading slots, and contractor margins. Three of those interact non-linearly. If you model one variable without the others, you get confidently wrong answers. If you model all three, the spreadsheet gets ugly.

The uglier the model, the harder it is to sell upward. The harder it is to sell upward, the more executives push for the summary. The summary is where $100M in savings goes to die.

What shipped

I wrote the summary they asked for — but only as a read-out of the model they didn't. Six tabs, three thousand cells, one-sheet dashboard that surfaced the three interactions that actually moved the P&L. When the executive took it into the capital allocation review, what got approved wasn't the summary. It was the bet the summary represented.

The model itself is still referenced in their review cycle three years later. Not because I wrote it well. Because bothering to build it at all revealed the parts of the business they'd been flying blind on.

The operator takeaway

When a model feels too complex to build, that's usually the sign it's worth building. The executives who want a summary aren't being lazy — they're being rational about their time. Your job is to collapse the complexity honestly, not remove it. A good summary comes from a bad-looking spreadsheet.

If the model is small enough to hold in your head, the business is too small for it to matter.

This post came out of a fractional engagement I ran in 2023-25. For the full write-up of that project, the case study is here.