Give me 5 examples of a starting QB on a contract like Kyler has being traded and what they got. You can't because it rarely happens. Darnold was traded after 3 seasons, the third of which was the worst of his 3 years. They literally traded him to make room for Zach Wilson, that's how little the Jets thought of him, and they still got a 3rd.
If Murray doesn't completely meltdown the rest of this year the Cards will be able to trade him but how he does the rest of the year will determine what we get in exchange. Acting like anybody knows in early october what that value is, is just wrong. Nobody knows.
The situation the Cardinals have put themselves in is rare. A QB that has never done anything of note getting paid what he does and then the team wanting to get out of it is something pretty unique.
But there are some similarities we can pull from other trades. The Mayfield trade was a conditional 5th. His team were sellers, having already traded for Watson, that weakened their position. And Mayfield was younger with more untapped potential.
Kyler's situation is far closer to Brock Osweiler than any of these, where the Texans had to pay to get rid of his contract. I'm not saying he's Osweiler, but the situation is closer to that than say, the trade of Alex Smith from the Chiefs to Washington which was for a 3rd. Smith had a long track record of winning and was a proven NFL QB.