The cost of a Tunnel Boring Machine (TBM) varies significantly based on factors such as size, type, customization, and project requirements. Here's a general overview:

　　1. Small TBMs: Designed for utility or subway tunnels, these machines typically cost between $1 million and $10 million.

　　2. Medium to Large TBMs: Used for substantial infrastructure projects like road or rail tunnels, their prices generally range from $10 million to $50 million.

　　3. Specialized or Very Large TBMs: For major undertakings, such as undersea tunnels, costs can exceed $50 million, sometimes reaching up to $100 million or more.

　　An industry guideline suggests that TBMs may cost approximately $1 million per meter of diameter. However, this is a rough estimate, and actual costs can vary based on specific project needs and machine specifications.

　　It's important to note that these figures represent the base cost of the TBM itself. Additional expenses, including transportation, assembly, maintenance, and operational costs, can further influence the overall budget of a tunneling project.