The trade values site REALLY struggles assigning values to young prospects that haven't yet made a significant contribution in the majors. Having a value on Ruiz of roughly 4 is a joke, especially after the breakout he had and the fact he was traded as a major piece for the top relief arm in the game a few months ago. Yes, perhaps the Athletics had an uncharacteristic high value on him, but obviously so did the Brewers. And those are two teams who are generally well run and are pretty spot on with player evaluations much of the time.
I get the feeling that opinions here are skewed on Ruiz because of the Hader trade fallout. People want to think that the Brewers were fleeced in that deal because they need justification for their anger. But in reality, Ruiz obviously holds a high value, and the Brewers likely did pretty well in that deal, picking up what now looks like two very high-end prospects in Ruiz and Gasser.