Repair cost for Beats Studio Wireless?

I currently have Beats Studio Wireless, I bought them a while ago when Apple was just purchasing Beats. I tried to enter my SN into the Apple Warranty site, however it's not showing up, it's saying that it's a invalid SN. The cushions on the Beats are just broken, they're still intact, however I would love to get them fixed. How much would it approximately cost? I believe I'm out of the warranty