The problem is to know what to write. I spent a whole day yesterday to understand what the problem was with a PDF file we were failing to process. Once I understood the cause it took one line of code to fix it and another dozen of lines for a unit test. A LLM helped me to write the code to explore several possible candidate problems but it did not find the problem by itself.

So code is both cheaper (what the LLM wrote for me much faster than I could have typed it) and is also expensive (the only line that we deployed to production today.)