I can sit down and estimate how much my code is going to take (including the cache misses and other nonlinearities).
The way I earn money is by programming python. Why is it so? Because it's a cheaper solution and because you know that there's a multitude of libraries in Python that already do that for you. Optimisation is the overhead where you hire a developer solely to sit down and optimise; and quite frankly it is quite commoditised in that sense.