Amazon will reimburse arbitration fees if you win making it a cheaper option for consumers than small claims court.
"If".
[Edit, because one-word replies are uncivilized: one reason to be suspicious about binding arbitration is that the company against whom you'll be pleading is a repeat customer of that arbitration service. It's a non-transparent / non-public process, so it's hard to have confidence is fair, and over which we (ie, the public) have no influence if it were not.]
It's 75 bucks in the EU without waiting for the reimbursement.
Two problems with that argument: 1) Amazon would also have to reimburse small claims court fees if you win, and 2) arbitration is worse for the consumer in pretty much every other way.