Another way to do value based pricing is to set a license fee proportional to the amount of volume pushed through the software. That license fee would need to be figured out from the business context and some estimate of how much value the software adds, and what alternatives the customer would have to perform the process without that software.

E.g. for bespoke process optimisation software sold to a single huge enterprise customer I've seen a $xxxx fee per "batch" that the software processes, plus an additional annual fee for maintenance and support.

The concept of "batch" was domain-specific and related to the customer's goal, the software might need to be run 1 or 100 times in order to complete a single batch (with user intervention etc to tweak parameters or correct input data errors), it wasn't simply $xxxx per API call.