I don't care bout cost, I care about getting good results fast.

Cost per line of code is not a suitable metric for anything. It's as silly as measuring engineers' performance by lines of code. More lines of code is worse than fewer lines of code. When you say "we have verified" whoever that "we" is makes a big difference, but you're posting pseudonymously, how are we to even guess at that "we"?

I get better results with some older cheaper models, faster. In particular older Claude models than Opus 4.7. Maybe the more expensive model churns out more lines, more complexity faster. That is a worse outcome for me. The complexity must be avoided at all costs. The simpler, smaller, answer is always better, and scales to bigger code bases. The more the model guesses at intent rather than checking intent, the more the model is clever rather than clear and simple, the worse the outcome, the more that the model turns into an architecture astronaut, the worse the outcome.