Civility costs nothing, and buys everything. 礼貌无需代价,却能买到一切。——玛丽·惠特利·蒙塔古语言点:civility即courteousness,意为文明礼貌,即good manners;其反义词incivility意为:粗俗无理

cost意为花费,以...为代价;costly意为费钱、需付出代价

句中cost与buy意义对应,nothing与everything意义对应