I've been manufacturing an 8 GPU rig for a few months now, as a follow-on to 4 and 6 GPU open frame rigs I've been making for a few years... Initially this unit used Radeon 380s and now Radeon 470/480s. Some may have seen it listed on ebay, I sell some there but it's primarily for the exposure, most units are sold direct to large farm operators who are running 50+ units at a time.
I do sell to individual miners as well and have been doing that for some time as well, posting this to share some details on the system as I have had a few people from the forums ask me about them...
The units run a fully custom Linux load, or a customized version of ethOS depending on the end users coin, they can mine most anything as with any GPU rig, given how many GPUs are in the system I sometimes need to customize the miner or it's launcher so it runs properly.
Prices start at $3600 USD for single systems and go down under $3,000 as the quantity goes up.
ETH: 230Mh/s
ZEC: 1200H/s
Power Usage ~1150W on 220V+, 1250W On 110V
These shots are from my 380 unit, 470 unit almost identical minus change in cards, and some strengthening of the chassis in my latest model revision to better handle shipping...