The emergence of high penetration rates of renewable energies in power systems presents a serious challenge in energy generation and load balance maintenance to ensure power network stability and reliability. Energy Storage Systems (ESSs) could play a relevant role in facing these challenges, as the technologies have passed the demo and prototype phases to a wide market implementation phase. The only remaining barrier for their implementation is their cost, but even this barrier is quickly disappearing. In this paper, we address the financial feasibility of storage technologies in electricity systems. In particular, we evaluate whether such technologies are economically sustainable and how far they are from becoming viable. For this purpose, we consider the Chilean electricity system and evaluate the maximum possible arbitrage revenues that could be achieved under ESS through benefiting from energy time shift, diminishing of transmission losses, and transmission upgrade deferral. The results show that the arbitrage revenues are still below the cost of storage systems. Further improvement in storage efficiency or a decrease in the cost of storage systems is still needed to make this type of investment financially viable in the near future.