The Distribute Travel MultiBrand API is charged on a usage basis, and uses a concept of 'API Units' to determine the monthly fees for using the service.
API users sign up to an agreed monthly usage rate (typically £x per million API Units), and your usage is tracked on a request by request basis. Every API response includes a <Cost> node detailing the number of 'API Units' consumed by the request, allowing you to internally track costs on an ongoing and real time basis.
'API Units' are typically based on the complexity of the search and a number of other factors. Complexity is determined primarily by the number of departure dates specified in your search. For example, a request for departures over a whole week to a single Destination would incur 7 times the amount of 'API Units' consumed by a request for departures on a single day.
Further to the above criteria, the cost is also multiplied by a Supplier specific rate dependent on the complexity of obtaining data for the requested Destination. Typically, searches for larger areas (for example a country level search) will have a larger multiplier, although this is not always the case. A detailed breakdown of this Supplier specific multiplier for each Destination can be provided on request.