the linked article didn't seem to explain the index well. I can't tell if that's a deficiency of the article or the index.

Other than the fact that this is related to Musk, I don’t exactly see how this specifically relates to Space Exploration

I’m voting to close this question because it doesn't seem particularly space related

@AlanBirtles ... please see edit and consider re-opening the question.

Even if it was space related, it's asking for opinions.

@OrganicMarble ... questions in economics and business management can (and should be) be supported with quantitative evidence, just like engineering questions. If an ANSWER is opinion based, it can be downvoted. Closing a question because you may not like someone's answer is like shouting down a speaker in a meeting.

You mean, like calling something idiotic?

@OrganicMarble ... exactly. Elon uses the word for his index name, implying that anything high on his index is idiotic and, by implication, anyone who created or supported the design, an ad hominem fallacy. I used the word in the post as a parody of Elon's use in the index name. Elon is obviously not an idiot, so to avoid offending Elonophiles i will edit it out.

I think this is an interesting question, whether its best here on another SE site I couldn't say though I think its worth keeping open here to see if anyone comes up with some constructive response.

I haven't voted on this question at all, and I despise Musk (and have since before despising him was cool), but your question as written asks "why not" Musk didn't pick a different metric instead of inventing this one. Not answerable. Possibly salvageable by revision.

In Walter Issacson's book about Elon Musk he tells a story that he witnessed first hand where in a meeting with the person in the finance department who oversaw the Raptor engine costs Musk threatened to fire him because he couldn't off the top of his head name the top idiot list items on the Raptor, and refused to let him look at his computer screen to find out. In a meeting the next day the employee presented a list which showed that machined parts were high on the list and that this was an area where improvements could be made, and Musk was pleased.

That sounds like a very complicated way to get to "reduce machining as much as we can" which is like. Standard practice when upscaling from custom made prototypes to line production.

@DarthPseudonym I think there really is something here. Traditional rocket manufacture didn't really think of cost reduction, and larger volume manufacture like aircraft (sadly) embraced cost minimization at every imaginable point, the comparatively low volume for SpaceX combined with the urgency to identify and reduce the major contributors to cost seems to be a unique situation. There's nothing comparable in terms of cost, volume, reliability, and especially time pressure.

@DarthPseudonym And I think this is exactly opposite of very complicated - it's s quick way to nominate the nail that's probably sticking out the furthest without a full-blown cost analysis so that it can quickly get hit. voting to reopen to provide an opportunity for good answers to be posted. Just because five people can't think of a good answer doesn't mean nobody can.

The high-level point is good. I feel like the question breaks on the last assumption, "Since what matters is overall production cost, why not just look at that instead...?". What matters is "the mission's value proposition to its stakeholders". So, for a science mission, the stakeholders might be the taxpayers, but for a commercial enterprise it could be about how well a decision supports the overall business model. Does this really boil down to "production cost"? I think it's defined by a far more complex set of trades. So, could production cost just be a lesser oversimplification?

@Woody "Elon is obviously not an idiot" citation needed.

It's subject to Goodhart's Law (Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.) It's good for identifying places worth optimizing, but should never be a goal by itself; like substituting raw material with more expensive for no real benefit. "Looking at overall production cost" would mitigate some misuse of Idiot Index as a goal metric, but reduce its usability in its intended purpose.as bottleneck identification tool. The same misuse can be mitigated by intelligent and careful use of Idiot Index without the trade-off.

@StarfishPrime ... could not find citations for Elon's absence of idiocy. Even if absence of evidence is not evidence of absence, this is a bit worrisome.