I recently tasted two 2013 McLaren Vale Shiraz wines side by side in a miniature "Do You Get What You Pay For?" exercise.
I'd managed to source the Gemtree Uncut Shiraz at the bargain price of NZ$19.99 against a usual price of $30 to $32. The bottle was not decanted - I would however recommend doing this both for aeration, and because the wine has thrown some sediment. The wine spends 16 months in French oak barrels froom 225l to 500l in size, with minimal racking and was bottled unfined and unfiltered. There is quite a lot of oomph in this wine; on the nose there is plenty of fruitcake, licorish and spice. Upfront the palate is ripe and juicy, then a line of bitterness develops and the ripe tannins come to the fore. 
D'Arenberg Dead Arm is a wine which features in my wine collection, though I have no vintages after 2004. The 2013 is a much juicier, supple, less oaky wine than my recollection of tasting those earlier vintages. This wine, at NZ$58 to $62 is around double the (usual) price of the Gemtree. Here the ferment begins in open top vessels with foot treading then after basket pressing the last third of the ferment takes place in new and used French and American barrels. Some descriptions of the winemaking which I have seen suggest only a portion of the wine remains in barrels throughout the maturation. On the nose the wine is higher toned with aromatic wood and licorish. It is even juicer than the Uncut, with brighter flavours of red and black fruit, subtle oak and well-balanced acidity. There is a stripe of grainy tannin across the tongue, but overall this is a more polished wine than the Uncut. The finish is very long, and again higher toned characters are noticeable. 
This was a very pleasurable return to Dead Arm. The suppleness, brightness of fruit and length of finish do mark it out from the Uncut. But event at $32 the Gemtree wine is very fair value. And at NZ$19.99 it is an absolute steal. Hunt around on wine-searcher.com if you are in New Zealand - at the time of posting Wine Central still have this wine at this great price.