If people could travel at the speed of light, it would have profound implications for various aspects of life, but it's unlikely that it would directly translate into a form of currency.
Currency typically serves as a medium of exchange, a unit of account, and a store of value. It represents a mutually agreed-upon system of value that facilitates trade and economic transactions. While the ability to travel at the speed of light would be an extraordinary capability, it does not inherently possess the characteristics necessary to function as a currency.
Currency needs to be divisible, fungible (each unit is interchangeable), and generally accepted as a medium of exchange. Speed of light travel does not have these characteristics. Additionally, currencies are typically based on trust and institutional frameworks that regulate their use and value.
However, it's worth noting that advancements in transportation and communication technologies can have an impact on economic systems, trade, and the way we conduct transactions. The ability to travel quickly and communicate instantaneously across vast distances could reshape industries, create new opportunities, and potentially impact the value of certain goods or services. But this would be more related to the broader implications of such technology rather than directly using the ability as a form of currency itself.