The standard process of creating a Kubernetes Cluster, requires the user to be aware of workload and infrastructure components for their application. These includes configuring the number of nodes required, machine type, VPC, network configurations, security configuration, etc. For details on standard step, refer to this article –Create A Private Instance Of Google Kubernetes Cluster
Usually the workload requirements are not known, so you either underprovision or overprovision the nodes and cost of running the GKE cluster is equal to number of running nodes.
With GKE Autopilot, Google cloud takes care of infrastructure and dynamic provisioning of cluster nodes based on your actual workloads. You just need to deploy our pods. Also, with GKE Autopilot, the cost model shifts to number of pods running and how much resources are being consumed by your pods.
GKE Autopilot reduces the overhead of maintaining the cluster, optimizes your infrastructure and cost based on actual workload usages.