Turntable versus tonearm versus cartridge: which is MOST important?

Up to some point the platform, that is the turntable and arm, are the most important because if the basic foundation is not solid then the cartridge can't perform well.  That should be obvious.  But once that critical point is reached, then the relative importance of the pieces would shift it seems to me.  We could argue about exactly where the change over occurs forever, but in principle it should be possible to agree on this basic formula. 

This one is easy. The $500 cartridge on the better turntable. It is easy to make an expensive cartridge sound terrible, much worse than a $500 cartridge working at it's best.

though I realize not everyone here will agree, and most do agree that "everything matters", I strongly believe that the areas of analogue reproduction involving the conversions of mechanical to electrical information, and vice versa, are the likeliest areas to create changes in  perceived sound, ie, tonearm/cartridge/turntable, and speakers/room...my experience also dictates what Millercarbon says above, you want the cartridge to get everything from the groove but nothing from the outside world, so a good cartridge w a great arm and table usually surpasses a great cartridge with a lesser table and arm....