> I never thought this type of work was particularly hard or expensive though.

Maybe not intrinsically hard, but hard because it's so boring you can't concentrate.

> the LLM becomes a helpful tool but requires a ton of guidance. Even the tests LLMs will write seem biased to pass rather than stress its code and find bugs.

ISTR some have had success by taking responsibility for the tests and only having the LLM work on the main code. But since I only seem to recall it, that was probably a while ago, so who knows if it's still valid.