Honestly, it's not a big deal, and I would totally do this if I hadn't already bought this lanyard LOL. (Finally found a way to combine my two geeky interests!)
Last I heard they were $4.95, but wouldn't surprise me if Royal raised the price LOL. I'm intrigued by them, and I guess a lot of the DIS board members are used to using the MagicBands at WDW.
We just had them punch a hole in the cards and hung them from the clip. Unlike the Disney ships, RCCL (for those that don't know) require you to insert your card...so it all worked out...
As a side note, you cannot punch a hole in Sea Pass cards for Quantum class ships (Anthem, Ovation, Quantum) and Harmony, Symphony of the Seas as they utilize the RFID technology. You can see the technology in action in this video from Quantum of the Seas.