I interviewed for a data position at a major internet clothing store last year and they said their return rate was in that ballpark. (I don't fully remember the number)
Clothing has higher than average return rates because people can't anticipate sizing or look. I worked for a food ecommerce site and our return rate was low single digits.
I prefer being publicly anonymous and if I answered your question there is literally only 1 person I could be. I suppose that makes me paranoid but I'd rather not create drama.
For the sake of example, Amazon.com would be sufficiently equivalent as we do sell products via Amazon. And the fact I complain about Amazon in places gives away that we do do that. :P