Turntable versus tonearm versus cartridge: which is MOST important?

IMO to deduct from price about quality is difficult especially in audio. So comparison only on price is even more difficult.
Although I haven't heard very cheap cartridge which plays very good on any system. If there is problems to discriminate good MC or moving iron from AT-VM95E - there a problem with a system but it doesn't mean that it's a problem with a price of  AT-VM95E

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.

It is also easier and usually much less expensive to upgrade cartridges down the line than turntables. Even the best cartridges will wear out. The best turntables will not.