Alright I managed to watch a bit of tape on this, and here's my thoughts (after a diatribe about Tony):
First, yes, don't bet against Tony Ferguson at LW. Ever. (Okay "ever" is extreme, but at least not until he shows signs of slowing down). Not even if he fights Khabib. (Esp given Khabib will be around -200 or so if he beats Dustin convincingly). Ferguson really is a next level fighter, and that's my completely objective evaluation with zero bias whatsoever LOL. But seriously, the things he brings into fights you cannot replicate. He does serious damage to EVERYONE he fights. And because he doesn't get tired, that damage increases as time goes by. He is a special fighter, and people have failed to realize just how uniquely talented the guy is for a long time. Betting against this guy is a good way to lose $, and has been for every fight for the last SEVEN YEARS. That's my general betting disclaimer for today.
Now, Cowboy vs Gaethje. Gaethje is better than the "big dumb idiot with a chin who hits hard". But...yeah he's shown serious lapses in fight IQ at times because he absolutely doesn't care how much damage he takes as long as he can inflict some. But he does have a very good chin and will land hard strikes in every fight he's in because of his style. Which may not bode well for Cowboy. Because while Cowboy's durability is still okay, it's not what it was. And the beating he took from Tony pretty recently isn't going to help on that front. The other issue for Cowboy is that he loves, LOVES to try to set up his high kick with straight punches. Which is fine, but it means he has to be really heavy on his lead leg in order to generate any force with his rear leg. And if you watch tape, he is ALWAYS heavy on his lead leg. Gaethje is going to likely blast the hell out of that lead leg from the opening bell. And Cowboy will land straight punches in return. Watch Gaethje vs Dustin to see what this fight will likely resemble early on. Gaethje had Dustin limping from chewing up his legs with low kicks, but Dustin was busting up JG's face in exchange. The thing is, can you really be confident that Cowboy can inflict the kind of damage Dustin did in exchange for having his legs pulverized? I'm not.
So...betting the fight. I didn't check the odds before capping it myself (I like to first cap myself then check to see how they compare). I capped Gaethje around -200. And lo and behold, that's where he sits. So...hard pass imo at current odds. I think odds are spot on. Cowboy can win, but Justin a solid favorite and with good reason.