What is the correct rough estimation for the payload to kick-off a sustainable Mars colony?

In this talk, Elon Musk explains our current global capacity required to kick-off a sustainable Mars colony, should be about 1 000 000 tons (including humans).

While this is for sure just some rough estimate, I am curious how this payload of one million tons is calculated? (or another figure targeting such an estimate)

In 2016 he talked also about that there could be same number of people by 2060s on Mars. That would be, each colonist takes on average 1 ton of payload including him/herself, but that would mean, their payload is 100% self-sustainable which is hard to imagine, so maybe they would have 500 kg their own private and professional stuff and the remaining mass being power plant parts or road building machines etc.

Please share if you know actual facts beyond these speculations of mine.

QUESTION

If this payload would be calculated with an uncertainty between 100K metric tons and 10m tons, what method should be followed to include all items so that relevant interdisciplinary experts would agree that this should be with an acceptable human mission risk condition to be sufficient to kick-off a sustainable Mars colony?

UPDATE I do not even know whether there is a "bill of material list" to have an idea of a little bit more precise drill down with a pragmatic level of uncertainty. Following an idea from a comment below to start with heavy necessities:

• Ice mining equipment
• Solar panel manufacturing equipment
• Fuel production equipment
• Machines for road and landing area construction
• Machines for base habitat structure construction
• -> further things and things to produce things (with sufficient recursion levels) which make out a sustainable colony i.e. no supply required for critical goods

UPDATE2 This is not about how wrong or right is Elon Musk with his estimation, neither about what exactly makes a sustainable colony. It's the question about how such an estimate can be done to be correct i.e. in defined parameters window for the hypothetical total payload and acceptable risk level.

• You forgot vitamin C. What if the supply ships stop coming? In an interview with Eric Berger last spring, Elon Musk said that a million tons of vitamin C alone would be needed to make a Mars colony sustainable. Oct 26, 2020 at 10:18
• well million tons.. I can add vitamin C here but I thought "sustainable colony" means it could start producing vitamin C as well? this sounds in this case really figurative. Wikipedia: "Eighty percent of the world's supply of ascorbic acid is produced in China." - something about < 100k metric tonnes. Oct 26, 2020 at 10:26
• At what technology readiness level, J. Doe? I would not sign up for a one way trip to Mars when there is so much at TRL 6, or less, that is needed to sustain life. We do not know how to reliably and sustainably grow food on Mars, produce water on Mars, or produce breathable atmosphere on Mars. People seem to think that shouting "Sabatier process" solves all problems. The experimental Sabatier mechanism on the ISS failed with such great regularity that it is no longer used. Oct 26, 2020 at 11:08
• @DavidHammen this is an underlying question: "which TRL coverage is required for sustainability of a Mars colony?". Possible a risk-driven analysis could provide that. Also "TRL level influence on payload mass" is another aspect: does mean higher TRL less or more mass, and for which technologies? Oct 26, 2020 at 13:15
• Vitamin C -- presumably proper local agriculture , w/ solar-spectrum lamps to ensure proper growth, takes care of that. There are hundreds of organic and inorganic nutrients needed for healthy bodies; I can't imagine calling a colony "sustainable" if any of these need delivery for more than the first few years. Oct 26, 2020 at 13:51