Mistakes are expensive
Poor translations are much worse than no translation at all. Many people will forgive a site for not being in their native language, and will be willing to go to a translation site if they need the information; but if your translation is bad, they won’t trust you or your site to provide a quality product.
The discipline of translation suggests that full equivalence in translation between languages is rare. Misunderstanding doesn’t happen to qualified translators very often, especially if there is a proofreading process and a QA process involved as when using a translation service provider.
Correcting the translation mistakes is much more expensive than the initial cost of hiring a translation company from the outset.
A translation service provider will guarantee quality and deadline.