I took the bait and snagged one, it will arrive tomorrow, so basically ridiculously fast shipping. I had also read the reviews, ebay's got you covered for anyone that is skeptical about a seller like this.
You can get your money back, shipping included, extremely easily if you follow the procedures ebay lays out.
It's def one of those "to good to be true", but in the slight chance it is an actual brand new gray market 5dmkiii for that price? I will take it happily.
If it's reboxed, or anything off, it will just go back and ebay will be notified right away.
I will update my post here with the info for anyone who cares, fingers crossed.