We prebooked our tours from the cruiseship. So, I'm not sure how much the company will charge on individual basis. I paid US$35.
Although I signed up for the Gypsy Cove tour (by mistake, blame it on the purser), the 4W drive Lagoon Bluff tour would have been more interesting where you experience close encounter with the King Penguins. So, just make sure you are on the right tour!
The Gypsy Cove tour does cover the city tour of Stanley though. It's good, just not something I wanted!
The cruise ships all have to beach themselves in deep waters. So, we had to be transferred on smaller ferries to Stanley. It was quite a rough ride. The entire vesel had to be covered!