If you are wondering about the odd price structure, compare the price and the 2010 impact factor (from Wikipedia):
Nature $36, impact factor 36.1
Nature Biotechnology $31, impact factor 31.1
Nature Cell Biology $19, impact factor 19.4
Nature Chemical Biology $15, impact factor 15.8
Nature Chemistry $17, impact factor 17.9
and the list goes on! at least they round down...