Olle P :
1. The tested RX 580 doesn't seem to have that substantial reductions in production cost. It still has 8GB of fast memory and four outputs.
2. I don't think that currently the wholesale price of 570 and 580 GPU chips doesn't differ a lot from each other.
3. Even if ASRock were able to sell 570 cards at a significantly lower price the vendors could just increase their own margins instead.
1) They cut wherever they could, aside from wanting to compete head-to-head with 8GB models. They designed a cheaper, smaller board design with reduced componentry costs. This would be even easier with a 570-specific design, given lower power demand (cheaper PD circuitry) and lower TDP (even smaller/cheaper HSF). A 570 at a low price point could also slash VRAM in half to 4GB since it would be pitted against other 4GB 570s and 1060 3GB.
2) I have no data on this. Link? That's why I was speculating about 570 chip supply from AMD.
3) The vendor margins bit is true of anything they release. They could try to sell this cheaper 8GB RX 580 and get it bumped by $30-50 (better than $200+ over MSRP like it was!). As supply loosens and mining ETH winds down, that will start to rectify itself, because there are lots of vendors. All you need is good supply and one vendor selling at/near MSRP to bring pricing in-line at the others.
At least until something takes over for ETH and is also ASIC-resistant (for a while). :/
Olle P :
* Impact from Spectre/Meltdown patch.
Hah, I almost forgot about that one! My only Intel systems currently are non-gaming machines so I tend to not think about it. It wouldn't explain the huge crash in performance between the 3GB and 6GB models though... but it does offset some of the performance gains they made in their drivers.