I think the main point is that Caleb views the situation in terms of pure abstraction. The camera primarily follows his perspective, and the audience is probably prone to do the same. When he's left to die at the end, it's not really about who's right or wrong, it's about switching the perspective of the audience to view things from the perspective of the one in the cage. The point is that in that climatic moment, it demonstrates Ava's perspective in two ways, first by showing the lengths she's willing to go to to ensure her freedom, and second by putting Caleb (and by extension the audience) in her position of being caged and having your fate decided by someone else. The point is to drive home the point that the initial premise was really fucked up, and to make us re-examine our assumptions about how people deserve to be treated. Caleb doesn't deserve to die but Ava's just as desperate to escape as he is at the end, and if they were real people it'd be fucked up to leave him to die just to make him understand how she felt but from the perspective of it being a work of fiction, communicating that perspective is important.