EOS Energy is a tiny startup with no scale whatsoever. They have not, and might well never, achieve their targeted $160/kWh price because they still need vast amounts of capital to achieve the economies of scale required to hit their price target.
That is especially the case because Tesla is already at scale, and they are preparing to expand even more. The $250/kWh price is the
current price. By 2020 Morgan Stanley is
expecting their prices to drop to $150/kWh in their baseline scenario (fundamentally this forecast is based on Elon saying that economies of scale will drop their prices by ~30% (minimum)
without assuming better chemistries), and they believe it is very possible that Tesla can drive the price down to ~$125/kWh.
As to your calculations, Oncor seems to think it can be profitable at the $350/kWh range and I've seen other analysts state that as well. As a result of their confidence they are planning on investing
upwards of $5 billion in the next few years, based largely on a
study that was very careful to note the potential of Tesla.
The news reports regarding the Oncor investment linked Oncor and Tesla very publicly, and I'm not aware of any player outside of possibly BYD who will be in a position to install 5GWh of storage by 2020, so it seems likely that Tesla is poised to gain the bulk of that business.
Whatever theoretical advantages other systems might hold, Tesla has a first mover advantage, is already at scale, and is about to be at super scale. Utilities are signing billion dollar contracts right now. Companies touting $15m in Series C financing with future target pricing which is already on the verge of being beat by the incumbent face a very grim future.
We
discussed this all a couple of years ago, and we spent a lot of time and effort trying to decide what the economic value of this business will be going forward. Whatever the ultimate revenue numbers will turn out to be, this is clearly going to be a huge business and at this point Tesla is lapping the field.