Comment by cloudking

You should start higher than your small customer plan. Enterprise customers have larger budgets and you will most likely have to build enterprise-specific features for this customer and future ones. Factor in the cost of developing enterprise feature requests (extra security, auditing, reporting, saml/sso etc). Calculate a per user rate, but quote them as a single site license for their org, give them flexibility to add a certain amount of users per year before renegotiating renewals. Also starting higher will give you room to negotiate if they push back. Good luck