According to https://www.crossref.org/fees/#sponsor-fees, for sponsors, the fee is calculated as follows:
The annual membership fee you pay as a Sponsor is based on the total annual publications revenue, income or funding of all the organizations you support, whichever is higher.
Do we total the highest value for each client (e.g. revenue for client A plus funding for client B), or do we total each for all clients and choose the highest (e.g. revenue for all clients, because that is higher than funding for all clients or income for all clients)?