I find this hard to believe. Any time people write systems in a dynamic language, they inevitably run into issues as they scale, ending up wasting money (computers, electricity) and a lot of user time. This usually results in rewriting things over and over.

Performance is always important. If you can solve a problem in 10% more time using a performant language, then it makes sense to do so, and I've seen few problems that I can express in Python or Ruby (painfully slow) that I cannot express in C++ (highly performant) or Scala (moderately performant) in roughly that amount of extra time.