The easiest and most authentic way to tell if a pair of Dr. Dre headphones are real is to do the following:
Visit the official Dr. Dre beats website - http://beatsbydre.com/support/register.aspx and on the right select the model of headphones you have e.g. studios.
Then type in the serial number, this is found on the inside of the battery case which is on the left ear cup. To open the battery case simple press down, and slightly turn anti-clockwise, release and then pull open. Then enter your details as requested and if it is activated, the headphones are real.