Article ($32): http://www.nature.com/nature/journal/vaop/ncurrent/full/natu...
Preprint: http://arxiv.org/abs/1205.3909
Preprint: http://arxiv.org/abs/1205.3909
In any case, just read the preprint instead. It's basically the same.
"we believe the publisher adds relatively little value to the publishing process... We are simply observing that if the process really were as complex, costly and value-added as the publishers protest that it is, 40% margins wouldn't be available."[0]