Ello,

Considering it is near the battle sprite update, of which is likely to be accompanied by a Summer related event, many potential buyers for said box would de-stabalize its possible value.

I'd estimate its value at 4kce - 6kce for now.
It will decrease if a similar, related, or identical Summer event is released.
It will increase if no identical/similar Summer event is released.

So it will depend a lot.

Hope this helps give an idea of what to expect though.

Raptor-Zy