So, in doing a bit of research from a link in one of the other comments, this is lcos, levelized cost of storage. I understand that to be roughly equivalent to the marginal cost of using it, including the capex divided over the unit volume. That same article uses $125/kwh as the capex, which is in line with your (and my) expectations of the cost to install.

$65/mwh works out to $0.065/kwh, so that makes sense. Effectively you can read this as "it costs $65/mwh to store and then consume electricity using these batteries"