The digitalization of international payment and settlement infrastructures represents a structural shift in the global architecture of cross-border capital flows. Traditional mechanisms based on correspondent banking, multi-day procedures, and document-intensive verification are increasingly complemented or replaced by programmable systems such as central bank digital currencies (CBDCs), tokenized deposits, automated compliance, and smart contracts. This paper argues that this transformation is not merely a technical efficiency gain, but a fundamental reconfiguration of transaction costs with direct implications for financial stability and the scalability of cross-border green finance.