sonyxperiageek: If they play out sound then they aren't fake. :-)
But seriously, at that price point, you probably won't get decent headphones on eBay to be honest.. You might as well buy some $30 Sennheiser CX300-IIs on Amazon.com.
What evidence do you have that the ones on amazon are genuine?
Many people, myself included, have been shipped fakes from amazon marketplace vendors.
http://www.wsj.com/articles/on-amazon-pooled-merchandise-opens-door-to-knockoffs-1399852852