"COF: How much does costume reflect the inner machinations of the plot, particularly in a film such as Inception? For example, Cobb’s children are wearing the same clothes at the end of the story as they are in his dream ‘memory’ throughout the film. Is there something to be interpreted here?And with that millions of internet theorists suddenly cried out in terror and were suddenly silenced. Not me. The "evidence" throughout the rest of the film is too weighted in a particular direction.
JK: Costume design reflects greatly on the movement of the plot, most significantly through character development. Character development is at the forefront of costume design. The characters move the story along and with the director and the actor the costume designer helps to set the film’s emotional tone in a visual way. In a more physical sense the costumes’ style and color help to keep the story on track, keeping a check on time and place.
On to the second part of your question, the children’s clothing is different in the final scene… look again ...
Film Another Inception interview, this time with costume designer Jeffrey Kurland. You've seen the film by now haven't you?