Rates are determined based on the requested language, the context in which an interpreter is needed, geographic location and in some cases industry and mileage.
Every state has its own certification training programs for interpreters, which is why pricing may vary from state-to-state. Not all situations require an interpreter to have specialized training. Therefore, you may request a qualified interpreter for situations in which extensive credentials or vocabulary is not necessary. Lower rates are charged for qualified interpreters.
On the other hand, in the event of a deposition or court trial, a certified court interpreter is required. These interpreters go through extensive testing, and as such are compensated at a higher rate.
The same goes for medical interpreters. Medical certification requires the interpreter to be fluent in healthcare terminology and advanced knowledge of the field. Certified medical interpretation appointments are quoted at a higher rate and require a three hour minimum

Telephonic
Telephonic interpreting is priced at a one-hour minimum and always scheduled in advance.

Translation
Translation pricing is calculated based on language, project complexity, and volume of the project; generally, there is a minimum price for up to 1000 words and then a price per additional page of text.

Transcription
Transcription pricing is calculated at a fixed price for audio recordings less than 10 minutes long and then at an additional fee per minute after the 10 minute threshold.