I think it depends on your competitors and what your software does. If your competitors are still running their services but not you, you're bound to lose some customers. Also, regardless of that, you can easily be losing money while the service is down. For instance, if you have a food delivery app and it's down, while your competitor is up, people will just use the other app and you're going to lose money while AWS is down. Even worse, they may actually end up liking the competitor's app better, and you can even lose customers that way.

However, if you're looking from the point of view of an employee trying to justify to your boss why the service is down. I'm sure they'll be more understanding that's not your fault in this case. It's a risk they decided to take.