It is clearly true. Up until the AI boom, the vast majority of a typical tech company’s costs are software engineers. Now it may be compute costs.

It's not true. Even though the vast majority of a tech company's cost were engineers, they also all grew like crazy and made much more (and grew even more) than they paid in salaries. The OP is correct, if it was just about salaries. These companies would have grown far more and hired far more endlessly, but the complexity of software at that scale makes diminishing returns from hiring more.

If anything the push to use AI has made me more expensive as a dev so far. If im honest i am only slightly more productive but i also burn through tokens.