It wasn't actually very expensive in money, because I was still able to RMA the pair of fried drives, but it did cost me $30 in shipping, a month of waiting, a lost delivery via UPS, and tons of time dealing with customer support for both UPS and Seagate to actually get a second set of replacement drives.

On the bright side, the actual replacements that eventually got to me were both 2TB bigger than the originals. They didn't tell me about this, so I'm not sure if they silently upgraded me to apologize for the wait, it was an accident, or they happened to be out of stock and just grabbed the next size up.