Son: How much does it cost to get married dad?
Father: I don’t know, I’m still paying for it.
To pay for something = obviously in a literal sense this means to give money in return for a product or service, but we can also use “to pay” in a figurative sense, meaning that you pay for something you have done with personal suffering.
Why is it funny?
The son is asking about the monetary price of a wedding, but the father has answered ironically, implying that he is suffering as a consequence of getting married.
Are you married?
How was your wedding?