Turntable versus tonearm versus cartridge: which is MOST important?

$500 can get you a nice cartridge, it does not have to be something unworthy of a nice table.  You can then upgrade the cartridge in time.  It is far harder to upgrade the table or arm, unless both are purchased at the same time. 

When looking for that nice table, look for models that put an emphasis on the arm.  It is getting harder to find decent arms these days (a major OEM maker for a number of brands--Jelco--went out of business).  The arm will become quite important when you do upgrade the cartridge; many of the better cartridges are lower in compliance (stiffer suspension) which means they have a tendency to feed back more energy into the arm which has to be stiff enough to handle this energy and the bearings musst also be stiff enough not to rattle while being low enough in friction for their movement to be unrestricted.  

OP's question is purposely obtuse, as kingbarbuda points out.  Any real buyer would really ask "How do I apportion my $10.5K bundle to get the best sounding set?".  In that case there are environmental considerations to consider in the choice of turntable and tonearm, but clearly most of the budget goes there.  Nobody should buy such an expensive cart on that budget.  

@ mijostyn
Excellent point! 

@millercarbon. “Put your money into table and arm. Then cartridge.”

+1

I really had to think about this. I have owned only four or five turntables and twice as many cartridges.  But MC is right… every one of my “wow, that is incredible” moments have been the turntable / arm changes (I don’t buy arms separately), never a cartridge change. 

I might point out that 3-4 of us delivered the same opinion as MC, prior to MC's post.  Anyway, it's a comfort to know we are mostly in agreement.