  A model of open economics composed of producers and speculators is
investigated by numerical simulations. The capital flows from the environment
to the producers and from them to the speculators. The price fluctuations are
suppressed by the speculators. When the aggressivity of the speculators grows,
there is a transition from the regime with almost sure profit to a very risky
regime in which very small fraction of speculators have stable gain. The
minimum of price fluctuations occurs close to the transition.
