In B2B Saas, subscription license is the main source of revenue. But there are several sources of revenues.
Subscription fee – this is a fee customer pay based on some parameters e.g. Salesforce users pay by the number of seats, AWS charges customers based on API usage, some companies charge based on data volumes. For most B2B Saas companies, this is the major source of revenue.
Sample → https://calendly.com/pricing
Professional services fee – this is a fee that companies may charge if there are any services involved especially in the beginning such as design, rollout, migration, custom implementation, onboarding, change management and so on.
Premier support fee – Software companies usually provide support at no additional cost especially in the beginning stages. Customer can opt to receive premium service e.g they may want 24 x 7 coverage of support or they may want a better SLA (service level agreements) such as faster response times or higher availability. Sometimes advance support team may be required to work with customers to address complex issues. All of these are generally clubbed under advanced support or services fee.
Sample→ https://education.oracle.com
Partnership fees – Many software companies rely on partners to provide add on capabilities. Some are resellers or distributors. Some are software companies whose products are add on to the platform. Salesforce, Microsoft, Netsuite, Google Cloud and others charge an annual fee for the privilege of being in the partner club.
Developer platform fee – Similar to partnership fee, developers of 3rd party products also pay fee to access the platform.
Certification Fee – Some companies like Cisco offer certification for professionals, who pay fee to be certified e.g. Cisco certified network admin certification.
Event registration fee – Annual events are a big draw for customers and other vendors. Almost all companies have their annual events in big cities like Las Vegas, and they charge for customers to attend these.
Sponsorship fees – They also require other vendors and partners to cough up sponsorship fee in exchange for a booth and other resources and promote them.