How to treat changing cost?

[tenjaa]

What is the problem?
The cost of a service change from time to time. Savings by scale, inflations, ...
The spec of the catalog says

Periodically, a Platform MAY re-query the service catalog endpoint for a Service Broker to see if there are any changes to the list of services.

I feel like this is not precise enough for billing.

Imagine I, it is 15.6.2023. As a broker, I decided to increase my prices by 10% from 1.7.2023 on.

• Do I push this change now because the platform only queries it from time to time?
• Do I push it on 1.7. hoping that the platform queries my catalog daily?
• Do I push it on 2.7. because then the billing for June should be done?
• How do I inform my users about the change in advance?

Who does this affect?
I would say mainly platforms but also brokers.

Do you have any proposed solutions?
Right now I could think of two options:

• Clarify when the cost information are updated. Either by saying daily, each 2nd day of the month or never/must be triggered manually in the platform somehow.
• Make cost information versioned with a date. So I can say "until 30.6. it is x EUR" and "from 1.7. it is x*1.1 EUR"