They could scale to $10M without probably any extra staff, or maybe an extra SRE? It isn't Twitter: They don't need an army of bloat-adding squads.

I haven't read much of the article, but they claim early on that they have no marketing spend. Do they say later in the article what their sales, saas, and server costs are like?

They don‘t have a sales team, so no cost. So it‘s barely sone SaaS they use by themselves (e.g. slack etc.) and server costs.

As they are running very lean I expect at least 80% margin.