It would be interesting (but unlikely) to hear about the company's entire financial picture. After working in online fashion retail, it's clear almost nobody is making money, despite what their revenues are.
eg: http://www.nastygal.com/clothes/paisley-sky-overalls
$78 for overalls.
Or $65 for a bikini bottom -
http://www.nastygal.com/clothes/righteous-bikini-bottom
It wouldn't surprise me at all if their net margin is great (compared to most retail).
Edit: In the case of the 2nd piece, Nasty Gal probably isn't making much money on it at all. It's made in the USA (which is usually a higher cost item), and the direct from manufacturer price is 63 dollars. Thus, it's probably a drop ship item with a razor thin margin.
The business model for online fashion retail is for the founders to extract as much cash as they can for themselves while it's hot and leave investors holding the bag when it's not.
I would take any article about such a company with grain of salt. One thing these companies do well is PR. Getting media placement often comes easy for them as employees of magazines, newspapers and blogs are often into fashion themselves and are eager to run a story about something they are personally interested in.
Eventually they run out of high margin stuff to sell, because they literally run out of the stuff (in the case of vintage clothing) or their suppliers start raising their prices. Then they need to sell more stuff, which requires more employees, and bigger warehouses, which continues to eat at the margins.
There's also many copy cat fashion sites, since between 2009-present "fashion internet" seems to have been a trend for fresh MBA grads. I'm not really sure how they get started, but I'm pretty confident they also don't make any money.
what about the other 100 she purchased at $150 and still are not sold? I made the numbers up but you cannot use an extreme case and assume the same applies to all.