With a static typed programming language, there's always a cost of compilation time and expected problems with linking libraries.
I cannot tell you how many times I have started a project with a specific cause to solve a particular problem, only to find myself trapped in a massive trap of unknown, cryptic error messages in C++ madness that I had to decipher...until I have realized I have completely forgot what I was even doing!
Now with a dynamic language, I solve all my problems in no time, I deliver a prototype quite fast, and whenever speed is necessary, I can always fix it in multiple ways, for instance what Python currently offers me; in other words, I optimize my performance only when it becomes a bottleneck.