I'd say it's down to personal preferance and even experiance with the item in question.
That seller on eBay has been selling on there since 2001 and has 100% positive feedback, I doubt very much he's selling crap.
There's far too much of the attitude that if it's on eBay and it's cheap then it must be crap.... So what's that "opinion" based on? Fact? I doubt it!
Anyway, back to the point, I've bought that exact same package and just had it fitted. Everything feels much more solid at the front end and the garage that fitted it said they were spot on.
After all where else would you buy them from? A motor factors? Halfords parts department? Let your local garage supply them? Well they all buy in pattern parts anyway, so who's to say they'll be any better quality and you'd be paying more for them!