AWS PrivateLink establishes private connections between the internal network of the cloud environment and specific services or applications. This is cost-effective because it keeps the data within the Amazon network, avoiding the public internet which can incur additional costs. Although AWS Direct Connect helps reduce costs for on-premises to cloud data transfer, it's not the primary service for connecting to individual applications within the cloud environment. VPC Peering is used for interconnecting networks, but does not address application-specific routing needs. Internet Gateways and NAT Gateways facilitate public internet access and are contrary to the purpose of minimizing costs through avoidance of public routes.