When the used batteries start piling up, it's best for tesla if this system is already in place. Entirely possible that this will be new and subsidized batteries initially. They will need to find a use for the old car batteries.

Could be, but they're jumping the gun a lot if that's the main idea. Tesla sales didn't really ramp up until 2014, and the batteries will probably last at least 10 years in the cars themselves.

In any case, they wouldn't need to subsidize these batteries. $350/kWh is a pretty decent price, and consistent with estimates of what they cost in Tesla's cars.

The large packs are priced at $250/kWh which I think is the real news. That means their cost is very likely under $200. Don't think the other car manuf are close to that.