How high do cigarette prices have to go for you to quit smoking?
When will you quit smoking? =いつタバコをやめるの?
まずは値段とかなしの普通な聞き方です。
How much is too much for a box of cigarette? =タバコ一箱で幾らだったら高すぎ?
How much is too expensive/priceyと言う表現の方が意味が伝わりやすいかもしれませんが、how much is too muchの方が語呂がいいのでこっちにしました。
How high do cigarette prices have to go for you to quit smoking? =タバコの値段がいくらまで上がったらやめるの?
難しい質問をしますね!!