I have worked with many teams and found lambda to be by far more cost effective. Did your calculations include the time lost waiting to deploy solutions while infrastructure gets spun up, the payment for staff or developers spending time putting infrastructure together instead of building solutions, the time spent maintaining the infrastructure, the cost of running servers at 2am when there is no traffic. Perhaps even the cost of running a fat relational database scaled for peak load that needs to bill you by the hour, again even when there is no traffic.
Serverless as an architectural pattern is about more than just Lambda and tends to incorporate a multitude of managed services to remove the cost of managment and configuration overhead. When you use IaC tools like Serverless Framework that are built to help developers put together an application as opposed to provisioning resources, it means you can get things up fast and ready to bill you only for usage and that scales amazingly.
Serverless as an architectural pattern is about more than just Lambda and tends to incorporate a multitude of managed services to remove the cost of managment and configuration overhead. When you use IaC tools like Serverless Framework that are built to help developers put together an application as opposed to provisioning resources, it means you can get things up fast and ready to bill you only for usage and that scales amazingly.