eBay+PayPal AFAIK can be from 8 to 15 depending on category. But that's not comparable. PayPal gives up a large part of its fees to credit card processors, and eBay markets the products. What GAW does is more like a currency/commodity exchange, which have fees below 1% typically. For example CEX - which GAW doesn't want to be compared to, but let's face it, they are cloning it plus some gimmicks - and their fees are 0.2% IIRC.
Basically this looks like an attempt to curb the trading for some reason. Maybe they have the illusion that this will somehow keep the prices high, or at least give them a fat 10% margin on the secondary market, but it might backfire spectacularly. We'll see.