Hardware Costs per GPU

[WTFudge]

I know it varies a lot and many people are running 4 cards off one system, I'm keen to know what the average people are spending per GPU they are running.

This does not include the cost of the GPU itself or electricity, just the cost of the hardware to host (i.e. total cost of Mobo, PSU, CPU, RAM (maybe even a case??) etc).