It's worth checking, but often the transfers are not cost-effective. For instance, for my upcoming Tokyo trip, the quote on the RSSC transfer was $350. A taxi runs about $200. And the limousine bus less than $30 (though a taxi from the drop-off point to the ship will be necessary, the fare should not be more than the equivalent of $10). I do recall a trip years ago where the transfer, purchased separately, was about the same as a taxi ride. I suspect it's a question of whether they can run a transfer in a cost-effective manner.