At what point does rising GPU prices become an extortion racket?
Uh, the point at which Gibbo points a gun to your head and insists you buy a 4x SLI Pascal Titan setup?
Nvidia's profits are going nowhere but up, flagship graphics cards have always been a luxury good that customers have been willing to pay a premium for and this is a particularly attractive release cycle - the only upper limit on prices will be the bracket that they want to put the new Titan into.

