Ephemeral values
Values change all the time; markets go up and down. Exchanges many stages removed from any base value (like derivatives traded at microsecond intervals) begin to derive value from the exchange process itself. Valuing money based on money exchanges really does approach the ephemeral in valuation.
Since the financial bubble collapse beginning in 2008, criticisms of derivatives and derivative trading have burgeoned, but they are still traded. The exchanges of default swaps became so entangled that they threatened to choke the entire system of financial liquidity -- but after a little quantitative ease from central banks, they are still trading.