Explanation:

- The idiom "costs an arm and a leg" means something that is very expensive.

- Option 1: "easy to obtain" suggests something that can be acquired without much effort, which is not related to the idiom.

- Option 2: very expensive, is the correct interpretation of the idiom.

- Option 3: "rarely available" implies scarcity, not costliness.

- Option 4: "nothing to lose" means having no risk, unrelated to cost.