i got a $20 intake on ebay with $20 ship which works like a mofo!
instead of buying a $100+ intake i got this one and it works just as goood IMHO... cost hell of a lot less too. Made of the same materials, filter looks the same as the K&N... makes a bad ass sound whenever i rev the car and i am totally happy.
I think it's different for other types of intakes such as the CAI since it would rely more on materials used to actually make it an authentic CAI... most copy cats just use long pipes and that's it... and they're still pretty pricey for copy cats $70+
...also i got burned on ebay a long time ago for buying a cheesey intake which kept on falling off.... and i also got a indiglo light gauge which was very cheesy because it didn't fit properlly even though it was supposed to be for my car! Augh! the price you pay when buying on ebay...