Crap welds and economies of scale aside....
I'm curious how different the sound might be with that relatively inexpensive DP vs. the full race/others. That could be more of a make or break for people than cost. It could sound great or like total raspy nasty exhaust leak. Also, cat/no cat options? Some people won't run without just cause of emissions and such. Being from NY originally I wouldn't take the chance or the hassle of swapping for the yearly inspections up there.
Also, the OP did post a link to this DP for really inexpensive on ebay and a link to it on the rev9 website for $300. I can definitely appreciate him at least pointing out a cheap option and showing us a ridiculous markup. Hey, it may not hold up the way the other ones will but dang, if i could get the same part for $180 instead of $300 id be pretty pleased.
I still don't think I'd run this though. Let us be proved wrong and it makes a ton of power. hahaha