If the price seems too good to be true, it probably is.
Quality 1000W+ PSUs usually cost over $120. I seriously doubt an eBay-only $70 PSU will be up to snuff quality-wise.
And mere 80+ certification at 1200W? That means as much as 300W wasted in the PSU assuming it can survive getting loaded all the way to 1200W - which nobody seems to be expecting it to based on the few comments I read about it elsewhere. This much heat in such a small space would be difficult to get rid of and no good for long-term reliability.
If you are building "high-end", you might want to stick to broadly reviewed and approved stuff instead of shaving corners with unknown, unreviewed home-brand eBay parts.