Since FullCalendar is an open-source JavaScript calendar framework, you can present potential alternatives that might offer similar functionality. Emphasize that you have received competitive quotes from other solutions that may meet your needs at lower costs. Make sure to highlight how they compare in terms of features offered and support.
If the contract includes any fees for additional features or usage above a defined limit, negotiate for those to be eliminated especially if your project sizes have varied. By referencing that you have had similar experiences with other suppliers offering more predictable pricing models, leverage that to seek a waiver on overage fees.
Offer to serve as a reference or be part of case studies for FullCalendar as a form of support to help them promote their software. In return, request price concessions. This mutual benefit approach could facilitate a more favorable pricing agreement.
Since your contract might automatically renew, ask to have this clause removed to allow for better negotiation leverage in the future. Explain that your finance team has guidelines that prohibit auto-renewing contracts without explicit approval, emphasizing this necessity.
Engage in a pricing gut check to validate the proposed price against competitive offerings or internal budget requirements. If the proposed rate is significantly higher than your expected budget or other alternatives, use this information to anchor your negotiation discussions.