GameFrame has its own form of play money, called FungiBills (from the word fungible, meaning “freely interchangeable”), which are used in several Frames and Powers. Among other things, these can be used to buy powers in the frame PowerBuyer.
To represent FungiBills, you may print the file available on this wiki (TK: need to add this), or use any form of play money you have available, as long as it is distinct from any play money you are already using. For example, if you’re applying the frame PowerBuyer to the game Monopoly, don't use Monopoly money to represent FungiBills, because then you can't tell the two apart.