…this is a classic case of predatory pricing: set your price low enough long enough to do real damage to competitors, and reduce their market share, not just immediately, but in the middle to long term.
Now admittedly some pet targets may not be hurt as badly as hoped. Russia will suffer more of an opportunity loss than an actual cost from the price reduction, since the ruble has fallen significantly against the dollar. The Saudis may hope to partially displace Russia as a supplier of oil to Europe (now roughly 1/3 of the total) but refineries would need to be retooled to refine the Saudi’s light crude, so it isn’t clear whether even what amounts to bargain prices will offset this cost (and readers point out that Russian crude may also produced a better mix of distillates for European use, since they are much heavier users of diesel fuel than the US).
But aside from the not-inconsiderable economic impact, the surprise Saudi step looks to be an even bigger geopolitical winner. The US and Riyadh have been at odds for over a year; the Saudis were particularly unhappy over the US failure to try to topple Assad last summer (you may recall the intensity of the Administration warmongering versus the dubious US interest; even Congress showed an unexpected amount of backbone and made its lack of support for Syrian adventurism clear). The Saudis have also long been less than happy with the US refusal to attack Iran (which is a rare case of the US acting as a responsible hegemon and curbing a putative ally with a bad case of blood lust). That unhappiness has ben compounded by the US now effectively helping the Assad regime and working in as distanced a manner as possible with Iran in targeting ISIS.