Oof, that's not even a $700 repair. What's pictured looks more like a $200 repair. The rest is straight profit for Electrified Garage, for having Tesla knowledge at this point in time. Personally, I would have used a plastic fitting so that if it were to get hit again, the fitting would take the damage instead of the part that has been threaded into. The driving force being this story seems to be that the owner didn'…
There's no way this is a $200 repair, that Tesla took up a bunch of shop time and their specialized technician for the better part of a day, carefully researching and installing this repair fitting. If you are charging $25/hr labor you are out of business.
If the repair fails, they will likely take it back and improve the fix.
Your plastic mystery fitting would likely not be compatible and cause a leak of whatever coolant is running around in there.
Lastly, road hazard insurance didn't cover any repair. Tesla doesn't do this kind of repair as well, leaving the only recourse replacing the entire part.