According to an Article in Greentech Media (read it here), financial advisory firm Lazard have released the results of ecomomic modelling they have performed on the levelised cost of energy storage for various technologies.
Lazard have modeled costs for a number of technologies in different application in front of the meter (network side) and behind the meter (consumer side). These results are displaced below.
The network side shows the costs coming close to grid parity in some instances, thought the consumer costs are still some way off.
The trend of decreasing storage costs is still continuing, so over time energy storage will only become more attractive.