I would offer $7000 for all 3 rigs, and that is still overpriced! Where on earth are you getting your sales price from?
There are 4 rigs. With 3 GPU's each. Total of 12 GPUs. And four 120GB ssd, and 4 Headless HDMI etc.
The sale price is the same price as the original on Ebay, but mine also come with all the extras
No one on these forums are going to pay Ebay prices. That rig is currently about 2x what the actual price is. If you want ebay prices, go sell on ebay, where you'll pay Ebay fees, paypal fees, and have to worry about buyer protections. If you want to be realistic, I would offer $2300 per rig.
EDIT: Or better yet, I would take just the GPU's since a 3 card rig has about double the overhead when scaling.