First of all, virtually no agency counts revenue like a Saas company (as “MRR” and “churn”), since the contracts most agencies sign are by definition not recurring. While some do sell retainer agreements, in general, the whole point of hiring an agency is to avoid hiring in-house for a need that isn’t ongoing or core to your business.
Second, there’s quite literally tens of thousands of agencies/consultancies that are over $50k in monthly revenue. All the big professional services conglomerates are constantly acquiring them (Omnicom, WPP, Publicis, Deloitte, EY, Accenture, etc etc) This is not a plateau that exists and the cited numbers are all totally made up.
Again, while it might be trendy on Twitter right now for people to try to sell “productized services,” this represents a minuscule percentage of the agency business. And agencies will never have true Saas economics, no matter how much they’ll try to tell you they do to get viral tweets.