It pops right up on NewEgg when I search 2133 in memory:
NewEgg: $54
A google search immediately drops you in at Amazon:
Amazon: $50
And I don't know how much you think the chips cost but the BOM from the 350 era if I remember was between $40-$60 for the chips (which were 175-260mm^2).
I see no reason why a PCB, 8GB of DDR3, a ~350-400mm^2 SoC, case, power supply, HS&F, HDD, etc. should be over $250. We can see if GPUs with much more expensive GDDR5 with 200mm^2+ chips going for $150. Yes the chip is bigger (so double the chip up to $100, so $50 more) and you need a PS, Case, HDD but you are also cutting out a number of levels of profts from various vendors and retail as well.
And the SoC size will really depend on what technology they are using for the "ESRAM". Cape Verde was like ~130mm^2 and a Jaguar core and L2 is like 8mm^2 each (~70mm^2 for 8 cores). Durango could possibly fall under 250mm^2 of 1T-SRAM or some more compact memory format (e.g. eDRAM although that seems unlikely due to the process).