I was sold a set of counterfeit Powerbeats3 headphones at Best Buy about a year ago. No reason to be suspicious initially, but battery life, range, and pairing were never great. They stopped working after a month, and I brought them back to Best Buy. The attendant looked carefully at the headphones and told me that they wouldn't accept the return because the serial number on the headphones didn't match the one on the box or receipt.

Anyone want to tell me how that could happen?

In any case, I called Apple, and they said that the serial number on my headphones was a duplicate and sent me a new set. Range, battery life, and pairing with the legit model are now all great.