Again, I am not suggesting trading for a Kawhi rental (especially not at that price). But if he is willing to sign an extension, then trading Fultz and Covington/Saric is perfectly reasonable for a top 5/10 player in the league.
Fultz showed flashes that he is a great at getting to the basket, which I think we already knew. He showed nothing in terms of shooting, which I think is what people were really wondering. Not to say that he can't get the form back and I am not trying to cast him off, it's just the price of trading for a top player.
Having said all of that, Kawhi's value is also lower than the earlier proposed trades. Unless he says otherwise, any non-LA team will be trading for a rental, which reduces his trade value.