The other side of the moon

In the early days, when you can't afford hardware, optimise for efficient code.

Sometimes this results in unreadable code or a language that not too many developers are familiar with. This is okay. You're trying to reduce the cost of hardware.

When you get large enough to hire other developers, the cost of hardware is no longer your largest expense. At this point, optimise for code readability.

This might mean writing slightly less efficient code or moving to a more popular language. That's okay. Developer efficiency is more important at this time.