Imagine what this means if you are trying to gauge impact of a post. Remember, X is giving them zero information about who they're preventing from seeing it. Impressions is the main datapoint so if you can't figure out why you've lost 98% of your impact, how on earth are you going to evaluate it vs other platforms?
And yes, each platform has a cost. There's a LOT more to social strategy than just "copy and paste this announce to every platform".