A translation is priced per 1,000 words of your manuscript: $1.00 for a production translation and $0.30 for a draft. You see the total before you start. A production translation takes the price in parts: a small deposit when the style bible is drafted (the price of the text it reads, counted toward the voice chapters), the rest of the voice chapters when you approve the bible, and the rest of the book when you approve the voice. If a stage stops part way, the credit for what it didn't get done comes back, and running it again charges only for what is left.
When the studio offers free samples, a production translation can start with one, once per account: the style bible and up to 3,000 words of the first chapters, translated, edited and checked, with their own QA report, at no charge. If the first chapters run longer, the rest of them is paid when you approve the style bible; the rest of the book, when you approve the first chapters. The price shows the sample before you start.