Here's a list of people since Exum who we obtained at less cost than Exum, but arguably outperformed him:
Joe Ingles
Rodney Hood
Shelvin Mack (even though Exum should have been playing)
Boris Diaw
George Hill
Joe Johnson
Jae Crowder
Jonas Jerebko
Thabo Sefolosha
Donovan Mitchell
Kyle Korver
Georges Niang
Royce O'Neale
Who would be an equivalent? I'd say Ekpe Udoh, but only because Ekpe didn't play enough. Obtaining more quality guys didn't appear that hard. We fed the delusion because sunk cost. But, ultimately, perhaps DL being so invested in this gave the illusion around the league of possible value.
So the most important thing is that he, somehow, returned us Jordan Clarkson. So that's cool. The only guys on that list above that are better than or equivalent to Clarkson's production/value are Ingles, Hill, Donovan, Royce and Crowder.