You are missing broader point here. If something is in production and burning cash, it can be replaced with optimised code if system are decoupled. But forcing optimisation earlier will make your developers less impactful and loose interest in the project or job. Most business logic code is updated frequently due to change in requirements and spending 100s of hours for feature which will be used by just small set of users is bad investment. This strategy can help you release some feature faster, get it A/B tested and once you have scaled enough you can start focusing on the individual decoupled system to be optimised.