Prices returned in API Rates is nightly rate for standard guests (maxGuest) of each listing.
If a listing allows additional guests, prices for additional guest will be given in additionalGuests which is provided by both API Listing and API Rates. For example:
In this example, 2 additional guests are allowed, and it is 15 EUR per (additional) guest per night.
Please note that all prices returned in API Rates are in EUR