Here's a short explanation for each phrase: "I'll take an arm": This phrase isn't commonly used, but it might be a humorous or exaggerated way of expressing that something is very expensive, similar to the idiom "costs an arm and a leg," meaning something is very costly. "What am I made of... money?": This is a rhetorical question people use to express that they think something is too expensive or to suggest that they don't have unlimited funds to spend. It's often said in a joking or sarcastic way.

Someone might sarcastically ask "Am I made of money?" to a person who regularly asks him to loan money or to buy things, or to someone who asks them for an unusually large amount of money. "Take an arm" doesn't have any specific idiomatic meaning, but we often say something costs "an arm and a leg" when it's really expensive.