Four million is definitely in the range of an outage at peak, that's not counting reallocated engineering resources to root cause and fix the problem, the opportunity cost of that fix in lost features, extra work by PR, potential contractual obligations for uptime, outage aftershocks, recruiting implications, customer support implications, etc.
If you have a once a year outage, how many employee-hours do you think you are going to lose to socially talking about it and not getting work done that day?
$116.6 Billion in revenue is ~13 million an hour. Outages usually happen under greater load, so very likely closer to ~25 mil an hour in practice.
> revenue wouldn't be lost if you had a 100ms outage
If that little blip cascades briefly and causes 1000 users to see an error page, and a mere five of them (0.5%) to give up on purchasing, boom you just lost those $700 (at least in the travel industry where ticket size is very high). Probably much more.
An error page can be enough for a handful of customers to decide to “come back later” or go with a competitor website.
If you think about experiments with button colors and other nearly imperceptible adjustments, that we know can affect conversion rates, an error page is orders of magnitude more impactful.
Probably, though when your business is making billions this is still just a few hours outage, or one long-running experiment dragging your conversion down by a few percentage points.
That looks like a value inflated by retellings of the popular Thomas Watson quote (see sibling comments).