Sets up a hypothetical for the sake of an explanation, and it is a favourite of anyone drawing a diagram in the air: [바이크가 있다고 치면] 오토바이가 이렇게 있잖아요 'say there's a bike here.' 치다 in this use means counting something as true whether or not it is — 없다고 치는 거야(?) 'we're pretending they don't exist?' It usually follows 예를 들어서 'for example', as in 예를 들어서 뭐 할인 행사가 있다고 치면.