Question

what does the idiom in this text suggest?
cell phones once cost an arm and a leg, but today the majority of people can afford them.
cell phones were once popular items to trade.
cell phones were once very expensive.
cell phones once varied greatly in price.

Explanation:

The idiom "cost an arm and a leg" means something is very expensive. In the context of the sentence, it is used to describe the past cost of cell phones.

Answer:

Cell phones were once very expensive.