Yes, we need to get data on the mileage under load. We know the unloaded mileage can be 500+, but what hit do you take with a trailer, etc.
A huge hit. The Model X in the article has a 5000 lb tow rating. Towing a 4400 lb horse trailer their range was cut by 2/3 over the the same circuit when not towing.
Watch the video, it is quite enlightening and surprising.