I am kind of unsure if these are "natural" indigo, in which I think you are referring to vegetable indigo.

I was looking on the BiG website, and they tend to say "pure" or "genuine" indigo, but the only vegetable indigo jeans are the ones labeled natural indigo. Of course the price reflects this since the natural indigo jeans tend to be in the 400-500 range, rather than the 200-300 range.