Mine was about $3500. My existing house service was 100A which was upgraded to 200A The wires out to the street were not changed, but the wires going from meter to the breaker box were, an entirely new breaker box was installed, so every single circuit in the house got removed from the old and connected to the new, which for many of them involved splicing in more wire. By comparison with the breaker box replacement, actually installing the Wall Connector was a minor part of the effort.
I think there were lower effort and cheaper solutions possible. I just wanted to give a real world example of paying that much.