What is a model in outsourcing that charges a variable fee based on transaction volume called?

The model in outsourcing that charges a variable fee based on transaction volume is commonly referred to as a "Method Model," which emphasizes that pricing structures can adapt based on the actual transactions processed. This flexibility allows companies to pay in proportion to their usage, making it financially advantageous, especially for those with fluctuating transaction volumes.

In contrast, a flat fee model typically entails a fixed price for services, regardless of the volume of transactions, which can be less favorable for businesses with varying needs. Meanwhile, a service level agreement is more focused on the quality and performance standards, rather than explicitly linking fees to transaction volume. Value-based models involve charging based on the perceived value delivered to the client, rather than strictly on transaction metrics. Thus, the dynamic nature of the Method Model aligns it closely with the variable fee structure described in the question.