There is more in a translation them simply the word count: the subject matter, complexity, how well it was written in the source language, etc: for instance, it is a lot easier (and so a lot cheaper) translating a love letter than a letter from a doctor to another describing a pacient's condition in high technically words. To give you a quote without seing the source document they would have to assume the worst and probably overcharge you. So, they want to see your letter to give you a fair price, not to scam you.
CAVEAT: I'm a translator myself and work for Hold in a regular basis
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