Xīn shǒujī yí shàngshì, lǎo xínghào jiù jiàngdào le báicàijià.
As soon as the new phone came out, the old model dropped to a rock-bottom price.
Tips
culture
Napa cabbage, 白菜, was the cheapest vegetable of the northern winter and was bought by the cartload, so 白菜价 means 'as cheap as cabbage'. Online shoppers use it for deals and price crashes.
