an arm and a leg vs unreasonable

an arm and a leg

noun
  • Usually used after the verb cost, but also often charge, pay, and spend: a very high price for an item or service; an exorbitant price 

unreasonable

adj
  • Without the ability to reason; unreasoning. 

  • Not reasonable; going beyond what could be expected or asked for. 

How often have the words an arm and a leg and unreasonable occurred in a corpus of books? (source: Google Ngram Viewer )