As Nita said, the corkage is standard. Not too high in my opinion.
If you like really good wine, it is actually a bargain. I know the wine we bring on with us (we have done it on HAL & NCL) would be considered their very expensive wine at $90+ a bottle. We paid in the neighbourhood of $30-60 on land, so with the corkage, a good deal. If you drink inexpensive wine $10-15 a bottle, it may not be worthwhile. Ships have a reasonable selection, but not great. They can't store wines properly on a ship. You will see some expensive plonk, but they may sell very, very few bottles in a year.
We have also bought the wine package, which was a reasonable deal for quite drinkable wines.