I was just thinking about this, and I think that the question is ill posed. If you compare the *wholesale* price of say, 3Sixteen jeans to the price you pay for say, Gustin jeans, they are about the same. Actually, 3Sixteen maybe making a bit less.
The real issue, and it is an interesting one, is what do resellers have to do in order to make the retail markup "worth it", however you may measure that. This is especially important in e-tailing, which has nearly none of the obvious benefits of B&M, with the exception being that a regular internet retailer, as opposed to a direct-to-consumer business, carries known brands which the customer trusts. For example, if I were to buy a pair of Common Projects sneakers, I have seen them many times already, I know and trust the brand, etc... On the other hand, if some direct-to-market business told me that they had the same sneakers, for 1/2 of the price, I have no guarantees I'm just flushing my money down the toilet.
I think that the next 5 years will be a very exciting time for retailers. Hopefully, they will have learned from the failure of the music business and the newspapers, and not assume that what they think the consumer wants, is actually what the consumer wants. I heard a reporter being interviewed on NPR say, "We assumed that people wanted all this wonderful journalism. Turns out that nobody really cared."