Translation is much more difficult that that. Many words have no foreign equivalent. Some phrases if translated word for word would make no sense or could be offensive. Cultures must be considered as well as specialized vocabularies. Translators are professionals in their fields of expertise.
Translation is expensive because it is very time consuming.
The time needed to translate a document could be greater than the time taken to originally create the document. Translators must find the word that most appropriately reflects the original meaning. This takes fluency in at least two languages and an expertise in a particular field. In addition, a translator must have a cultural understanding of the source and target languages and be able to combine this knowledge with grammar, writing and often research skills. The price of translation reflects the expertise and time needed to provide high-quality translations.