Yes, I paid the original shipping cost.
The bikes have been returned, and the majority of the refund also arrived except the part for original shipping.

I payed via paypal, then used my Discover card. I filed a dispute on paypal already. The thing is, I think Discover card might have better buyer protection policy, so if paypal dispute didn't work, I might go straight to Discover card instead of file a claim on paypal. That way, I can let my credit card company decide the case instead of asking paypal to decide the case.

It's my first time go through this, I don't know whether that's the right way to do it or not.

This might be a experience worth sharing since other people might face similar issues when purchasing online. So I will keep you guys posted if anything new happens.