NCL offers a pretty good wine list at acceptable prices when compared with other lines. Figure a reasonable bottle of table wine is going to run anywhere from $22 to $35. I always buy by the bottle because their house chardonney is lousy and their serving are quite small.
You cannot buy wine in the liquor store on board and drink it while on the ship, nor can you either carry or check a bottle of wine onto the ship. It will be confiscated and returned on the morning of your departure.