A complex subscription model goes beyond a simple flat monthly fee to incorporate multiple billing variables for a single customer, including base fees, usage charges, feature add-ons, and contract-specific adjustments.

Example: An enterprise customer pays a $2,000/month base fee for 50 seats, $0.05 per API call above 100,000/month, a $500/month premium support add-on, and a 5% annual price escalation clause, all within a single subscription.