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What's badly needed here is a sensitivity analysis.

For example, he lists ZocDoc's CAC as in the range $1k to $10k.

If it's $1k then their LTV/CAC = 4.8 (wow good!)

If it's $10k then their LTV/CAC = 0.48 (wow horrid!)

The author chose $3k, seemingly arbitrarily.

There's nothing wrong with arbitrary assumptions in general, but in this case a lot more scrutiny is needed before we judge if its a unicorn or donkey.

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When dealing with numbers that span orders of magnitude, it may be better to use the geometric mean (sqrt(1x10) approximately 3), not the usual mean ((1 + 10)/2 around 5). Just my guess.

I would argue that's no better.

I would say: When dealing with numbers that span orders of magnitude, and the result is very sensitivity to those numbers, you need to obtain more information in order to make a better estimate.

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