Do you have any actual data to back your wild assertions? Entire domains of computer science are dedicated to productivity languages and many are widely used with great success and little or no overhead relative to C. (edit: for example scipy)
I was stating an opinion based on my experience. I don't deny that tools like SciPy are very useful for experimental programming. However SciPy and Matlab are exceptions, where the end-user of the program is also the programmer, so the developer experience IS the user experience.
In most cases, when you are a professional developer, you are not the end-user of your product. In these cases, deliberately choosing a less performant language for the sake of developer productivity can mean you end up penalizing the end user.
