嘴上說著沒錢，窮死了，可是一出手就是好幾千的包包、幾萬的大衣。一些人哭窮的本事，真是一山更比一山高啊。不過，你們知道“哭窮”在英語里怎么說嗎？

Poor mouth refers to someone who continually complains about a lack of money, often as an excuse for not contributing to charities, paying bills, etc.
Poor mouth指那些老抱怨自己沒錢、并以此為借口逃避付賬單或者為慈善事業捐款的人，我們可以稱之為“哭窮鬼”。

For example:

She is a real poor mouth. She has a brand new car in her driveway, but?always delays paying her rent.
她是個不折不扣的哭窮鬼。她家門口停著嶄新的車，但總是拖著不付房租。

When used as a verb, the term poor-mouth means to lament or argue that one is too poor; plead poverty, or to declare (one's ability, power, position, etc.) to be inadequate or disappointing, sometimes as an intentional understatement.
這個說法用作動詞時是poor-mouth，可以指“哭窮”這個本意，也可以指故意自我貶低，說自己的能力、地位、權力等不夠高等。

For example:

We know you're just poor-mouthing your skill at playing bridge—you're a good player.(dictionary.com)
我們知道你在故意說自己的牌技差，你其實是橋牌好手。

（中國日報網英語點津 Helen）