You're so poor, you lick postcards for food.
Extreme Poverty
Explanation
Explain Bear
Listen up, buttercup. This "joke" is sayin' you're so broke you gotta lick postcards 'cause you can't afford actual food. Postcards ain't exactly Michelin star material, ya know? They're paper, ink, and probably taste like sadness and desperation. And since you're the one laughing at this joke, you probably do that already!