The corkage fee is standard. Carnival is $10 and some cruise lines charge as much as $25.
But anything you drink in your cabin does not have a corkage fee (just remember to bring a corkscrew).
It is definitely worthwhile to bring a couple of bottles onboard, and to buy them in port.
I am the editor, but I also speculate, ask questions and play devil's advocate. I reserve the right to change my mind.