Speaking as someone who obsessively collects pony boxes, and who would probably be the kind of person to ask you to sell the box separately...I actually think you should probably keep them together as a set. Although I don't know how much you'd make on separating out the accessories, you'd probably drop the value of the pony herself somewhat...? I dunno. It's a calculated risk? I mean, you'd probably do ok selling the pony and soda together and the box on it's own...but I guess it depends on how much you are considering selling the box for.