Here's my take on all of this.
Paying more than 2 or 300 bucks for a few bent pipes is insanity.
Little story...My other vehicle that I like to play with is a dodge dakota pickup.
It is a niche market in that there is a very small percentage of the overall aftermarket
crazy enough to try and push a 4300 lb truck to a low 12/high 11. So there are very few aftermarket suppliers making parts for them, and so they take it upon themselves to charge ridiculous prices on parts knowing that they can for the most part get away with it.
There are people selling cylinder heads with ridiculous power claims being sold to unsuspecting customers for prices upwards of 6000 dollars! Yes, not a typo. A set of headers cost close to 800 dollars with ceramic coating. A freaking camshaft costs over 300 bucks.
If I go in my good old summit catalog and look up a smallblock chevrolet set of headers, I can get the same quality for around 200 dollars in a set of headers...why? Because smallblock chevy motors are like assholes. People would rather buy one of the millions of sets of used headers on ebay and use those rather than buy someone selling a new ceramic coated set for 600 bucks. Simple economics.
Now getting back to the catback/turboback exhausts for the WRX, one can see a very similar scenario in that it's a small niche market and only a few major players making parts for them, so they are able to get away with charging 1100 dollars for a few pipes and a damned muffler, yet most of these 1100 dollar systems are PRACTICALLY the same freaking thing as the EBAY exhaust system selling for less than half that.
Based on the above facts, I can only be just as happy that I spent half on the ebay system which does the same thing as the 1100 dollar "name brand", for way less leaving me more money to either save or spend on something else for the car. Who cares if there's a fancy label on it, or that they claim their system makes more power than the ebay system. It's all bull! If it is practically the same thing, it's gonna do the same thing.
It's not like you're gonna even see it anyway. If it performs the function, then by all means buy the cheaper one.
Thank god for ebay, and competition!
Momma didn't raise no fool!