No offense but BS. What you have claimed is totally unsubstantiated, and not aligned with my experience working on highly-trafficked eCommerce applications.
If you know what your doing you can write elegant, performance tuned, secure and maintainable code in a dynamic language. I've also seen poorly written code written in statically typed languages.
It really comes to who is writing the code, what kind of standards they abide to, and their architectural prowess.