I don't think the realistic alternative here was “hire a team for a month and get a better semantic conversion”

For a rewrite of this size, the expensive part is deep understanding of the underlying system in order to preserve behavior while keeping performance, and above all that not freezing product work while doing it. Adding more engineers would just end up in managerial burden and review bottlenecks, to say the least.

So even assuming the API cost estimate is high, I don't buy the “just hire engineers for a month” take. A team unfamiliar with the codebase would probably spend a large chunk of that month just building context and deciding how not to break everything. A team familiar with the codebase is even more valuable doing product work, bug fixes, and review of the existing codebase.

So, in short, I do agree with the simple fact that this is still too expensive for most projects, but not with the idea that “a small team would trivially do better in a month”.