1. Which one is more common?
I cannot afford our trip fare.
I cannot afford our trip cost.
I'd like to know the difference and where you use fare and cost
---"trip fare" refers to the cost of the transportation ticket only, while "trip cost" includes any other charges such as food, hotel, etc.
2. a tour ship which is very large and luxurious inside, eg: Costa. What kind of ship it is?What kind of ship is Costa?
--- we call a ship like that a "luxury liner" or a "luxury cruise ship"