As much as this scene is about Thorin and his Crazy Faced Crazy Eyes of Crazy, the thing that I actually love the most is Bilbo here, and the things you know are going through his head. Because in that second-to-last panel he’s looking at fucking Smaug, and yet he still looks more frightened of Thorin.
As well he should be.
I’m agreeing with Smaug on this one. In the end, everybody goes treasure-mad over Erebor’s wealth except for Bilbo. All he wants is for his friends to get out of this mess alive. You can only consider him to ‘betray’ Thorin if you think Thorin is right to place more value on the Arkenstone than on the lives of the people who followed him here.
Thorin’s stated mission was to take back the halls of his grandfathers. Once the dragon’s dead, he has accomplished his quest. HE gets sidetracked—from the promises he made his own people!—by the Arkenstone and the wealth of Erebor. And for that matter, Bilbo is careful to make sure that the Arkenstone is never even really lost to him, but Thorin freaks out and threatens to kill him over it anyway.
In the book, as I remember, Bilbo goes down to visit the dragon twice of his own volition. After the second time, when he’s chased topside by Smaug’s fire, he refuses to go back down…until Thorin chases him back down at sword-point to go retrieve the Arkenstone. Absolutely right Bilbo is more afraid of Thorin than of Smaug—and how is that not a betrayal from someone you’ve come to consider a friend?