Select the most appropriate meaning of the given idiom.

Cost an arm and a leg

Be extremely expensive

The most appropriate meaning of the idiom "cost an arm and a leg" is be extremely expensive.

The other options are incorrect.

• "Be easily available" does not mean to be extremely expensive. Something that is easily available is something that you can get without much difficulty.
• "Be worthy of the cost" does not mean to be extremely expensive. Something that is worthy of the cost is something that is worth the money that you pay for it.
• "Be rather cheap" does not mean to be extremely expensive. Something that is rather cheap is something that is not very expensive.

The idiom "cost an arm and a leg" comes from the idea of something being so expensive that it is almost impossible to afford. In the same way, something that costs an arm and a leg is something that is very expensive. For example, you might say that a new car costs an arm and a leg.