Is sound leakage in studio beats by dre normal?

I bought studio beats on eBay, and everything seems legit except for the fact that they have horrible sound leakage. I turned the volume on my iPhone up only about a fifth of the way and my sister could hear it as if it was on a loud speaker. I've heard beats are notorious for sound leakage, but to what extent?

I feel that Beats are just an overpriced "accessory". If you want to real headphones buy from companies that specialize in audio products. Sure Beats are made by artist who make music. My friend recently bought these beat by dre, and the quality of sound is impeccable. And the price is very cheap.
headphones my friend bought: http://www.beatsbydresusa.com/