We normally say " We are sold out" when there are no more stocks left.
My question is "Is it acceptable to say 'They are or it is sold out' instead?"
Customer: Do you have that new video game?
Employee: Sorry, but we are sold out.
Customer: Do you know about the store across the street? Do you know if they have the game I'm looking for?
Employee: Sorry, I'm certain they are sold out too.
Employee: We are sold out, they are sold out, everyone seems to be sold out.
I don't know whether this is a BrE difference, but they are sold out sounds OK to me and they've sold out.