Well that's the theory, but Sonia threw a spanner in the works by stating the winner will take home $250k. There was no ambiguity there.They have said that there is a prize of $250,000 but it won't all go to the winner so you might be right, they will be tempted by cash and whoever takes the cash goes home and the other goes back into the game
ETA: I guess BB can change the rules at any time.