> The kind of place that thinks junior developers are cheaper than senior developers…

Unless the junior developers start accepting lower salaries once they become senior developers, that is a fact. Do you mean that they think junior developers are cheaper even when considering the cost per output, maybe?

I believe they're referring to the fact that if almost all of your code is written by junior developers without mentorship, you will end up wasting a lot of your development budget because your codebase is a mess.