NumPy is about one order of magnitude slower in very many situations. Cython is in some ways a reimplementation of Fortran in places -- I mean, you can consider it a better alternative but have to use features that are not in Python.

Personally I gave up writing numerical code in Cython and instead wrote it in Fortran and merely wrapped it with Cython...

But yes, being 2x-10x slower is something one can live with for productivity, vs sometimes 1000x slower of Python.