The plans are for 8) 750kW Tesla Semi chargers and 4) chargers for other semis. So, 12 chargers per location. Using the prices that we have seen for Supercharger installations it would seem like it would be about $5 million. (8 stall Supercharger, that is ~750kW, costing about $500k, so this is like a 96 stall Supercharger location in terms of power equipment.) They also may plan on installing some MegaPacks to help reduce demand charges, that could add another $5 million.
If it was sized for 750kW on all 12 stalls at once that would need a 9MW utility feed, which isn't going to come cheap, even if they went with power sharing and only installed a 4.5MW feed it isn't going to be anywhere near as cheap as a 750kW feed at a 8 stall Supercharger.
So yeah, $11m per site is probably about right.