  To the knowledge of the author, this is the first time it has been shown that
interest rates that are extremely high by modern standards (100% and higher)
are necessary within a zero-sum monetary system, and not just driven by greed.
Extreme interest rates that appeared in various places and times reinforce the
idea that hard money may have contributed to high rates of interest. Here a
model is presented that examines the interest rate required to succeed as an
investor in a zero-sum fixed quantity hard-money system. Even when the playing
field is significantly tilted toward the investor, interest rates need to be
much higher than expected. In a completely fair zero-sum system, an investor
cannot break even without charging 100% interest. Even with a 5% advantage, an
investor won't break even at 15% interest. From this it is concluded that what
we consider usurious rates today are, within a hard-money system, driven by
necessity.
  Cryptocurrency is a novel form of hard-currency. The inability to virtualize
the money creates a system close to zero-sum because of the limited supply
design. Therefore, within the bounds of a cryptocurrency system that limits
money creation, interest rates must rise to levels that the modern world
considers usury. It is impossible, therefore, that a cryptocurrency that is not
expandable could take over a modern economy and replace modern fiat currency.
