An example of how, for certain types of code, more than an order-of-magnitude performance improvement can be obtained with a good JIT compiler. I wrote a decompression routine (for a simple compression format) in several languages - it took the following lengths of time to run (normalized to C++ = 1 second):

* CPython, Jython, Lua, MicroPython, Ruby (1.8): >100 seconds

* Cython (naive), IronPython, Ruby (2.3): 50 - 80 seconds

* LuaJIT, PyPy, Cython (with type hints): ~4 seconds

* C#, Go, JavaScript (V8): ~1.5 seconds