Idiom of the day - Cost an arm and a leg Meaning: Cost a lot of money. Example: I would love to buy the new iPhone but it costs an arm and a leg. If you'd like to practice using this idiom, please write back to me on this post with an example and I'll tell you if you're using it correctly :D Finally, if you're looking for a friendly and patient teacher please check out my profile, my trial lessons start at $6. I look forward to meeting you. Thank you, Rianne :)