Hi @Đức Đinh Văn -- The cost isn't based per project. Infisical bills per identity at $18 each per month. An "identity" is anything that logs into your org, both human users and machine idetities (service accounts for apps, CI pipelines, Kubernetes, etc.). Your bill went from $18 to $36 because your org now has 2 identities instead of 1, likely a second user or a machine identity you added for an integration. You can see them under Organization → Access Control → Identities. It's counted across the whole org, not per project.
Please let me know if this clears it up. Thanks!