Those are NOT by any stretch of the imagination "GPU's". They are ASIC-based miners in cases that for whatever reason use a GPU-style of footprint. Stupidest idea ever....
I dunno from my perspective if they could leverage all 75W of the PCI-e port and deliver a ton more hashrate to match the bitaxe and other asics these could be a brilliant idea.
Looking at mineshop website mentioned by OP, the 6th image shows it has PCI power slot and connected to computer PSU. So the actual cost to run those miner is higher than some people expect.