I've been wondering about this for a while. Especially now that they're actively supplying servers to support sync (which also at least at the time of writing doesn't seem to allow running your own server).
But tracking is probably +5x more profitable minimum, while Vivaldi or Mozilla might get some $1/user Google probably makes $5-$15/user. And the reason of all the tracking and why companies fight so hard against legislation that try to cut their cash cow.