I have been on 15 cruises and have brought my own wine every time. I probably have been charged corkage 25% percent of the time.
That being said, I bring wine because I collect and love to drink wine. I have no problem with paying a corkage fee. The cruise line is probably making less profit on the corkage than they do on the wine.
I have found that when they realize that I have brought special wine, they treat it (and me) better. They will decant it. On Celebrity they told me to bring the wine down earlier so they could let it breathe. That's worth the corkage.