Meaning:
“家里” means “one’s family,” “有” means to “possess,” “矿” means “mine,” and “啊” at the end of a sentence implies this is a rhetorical question. Literally, this sentence can be translated as “Do you have a mine in your family?” As everyone knows, mine owners are often super rich. First appearing in a 2003 TV series titled “Ma Dashuai” starring comedian Zhao Benshan in the title role, this rhetorical question is often asked when one seems to be splashing money away mindlessly.
Example:
A: 我想买辆特斯拉。
Wǒ xiǎng mǎi liàng tèsīlā。
I want to buy a Tesla.
B: 你去年刚买了一辆车。这么大手大脚，家里有矿啊！
Nǐ qùnián gāng mǎi le yīliàng chē 。zhème dàshǒu dàjiǎo，jiālǐ yǒu kuàng a！
You just bought a car last year. You are extravagant with money, but do you have a gold mine in your home?