B HP Billiton, the world's biggest miner, has committed itself to spending $80bn (£50bn) by June 2015 on developing assets it already owns. The figure is so large it requires a yardstick: Xstrata and Anglo American, the world's fourth and fifth largest miners and top 15 members of the FTSE 100 index, are each worth roughly £45bn. Is BHP's capital expenditure spree evidence of a macho rush for growth? Well, BHP can certainly afford to spend $80bn. It is swimming in cash thanks to China's willingness to pay higher iron ore prices. Its other commodities, especially oil, are also mostly rising in price. The company has no debt and even a spare $10bn to throw at a share buyback. Commodity prices may fall long before June 2015. But a 2008-style collapse (unlikely) would have to occur for BHP's balance sheet to be stretched by the $80bn commitment. Note, too, that BHP was still generating healthy returns in 2008. A preference for building, rather than buying, assets is a welcome change of style.