Sticking with the theme of 'rich pop stars not knowing the value of money', Billie Eilish has admitted in a new interview that she thought a box of cereal cost $35.

To be fair to the 19-year-old, at least she's young. J Lo, on the other hand, should really know better.

Eilish made the confession in a new interview with Vanity Fair, where she revealed that she once ordered Froot Loops cereal to her house, thinking that one box would arrive. Instead, 70 small boxes turned up.

"I don’t know what things cost because I’ve never been an adult before," she said. And, you know, I grew up with no money. It’s a really weird position I’m in. I feel kind of stupid because I’m like, I don’t know how much Froot Loops are.

“I tried to order one box of Froot Loops and I was like, Oh yeah, sure. It’s 35 dollars (€28). I didn’t know that that’s expensive. I ordered 70 boxes.”

In the same interview, she also spoke about the attention that she had received concerning her body - specifically the paparazzi photograph that went viral last year of her in a vest and shorts, en route to the beach. Body shaming is something that she has been vocal about in the past.

"I think that the people around me were more worried about it than I was, because the reason I used to cut myself was because of my body," she said.  “To be quite honest with you, I only started wearing baggy clothes because of my body.

“I was really, really glad though, mainly, that I’m in this place in my life, because if that had happened three years ago, when I was in the midst of my horrible body relationship—or dancing a ton, five years ago, I wasn’t really eating. I was, like, starving myself. I remember taking a pill that told me that it would make me lose weight and it only made me pee the bed—when I was 12. It’s just crazy.

“I can’t even believe, like I—wow. Yeah. I thought that I would be the only one dealing with my hatred for my body, but I guess the internet also hates my body. So that’s great.”

Her documentary 'The World's a Little Blurry' is set to debut on Apple TV+ next month.