I found a question on Quora asking about the cheapest way to translate a document. My response follows.
You need to define "cheapest" as there are costs to cutting corners to get a less expensive translation. Sure, you can pump your text through Google Translate and have something in a target language. It might be accurate, and it might not. You can also farm out the work to the lowest bidder, but again, what are you getting for that low level of investment and how can you ensure they're performing a quality job?
True Localization Service Providers (LSPs) charge more to get the job done right. They use native speakers of the target languages who are extremely familiar with the local region for which you're translating and are familiar with the industry to which your information pertains. They have full-time project managers and QA staff who ensure the work stays on track and within budget for you and proof all work meticulously before sending it back to you.
Some LSPs also have authoring, layout, and consulting staff available to help you either produce your final product or proof your material pre-translation to ensure it's written well and in a manner that can be easily and accurately translated.
Translation is not about getting your content into another language. Translation is about providing the same quality of experience for people speaking different languages. The cost of shoddy translation is lack of sales, unhappy customers, and higher support costs, if not possible damage, injury or death due to poor translation of critical content.
Invest in getting the job done correctly the first time. You never get a second chance to make a good first impression.