agree vs buy into

agree

verb
  • To suit or be adapted in its effects; to do well. 

  • To make a stipulation by way of settling differences or determining a price; to exchange promises; to come to terms or to a common resolve; to promise. 

  • To consent to a contract or to an element of a contract. 

  • To be in harmony about an opinion, statement, or action; to have a consistent idea between two or more people. 

  • To give assent; to accede 

  • To correspond to (another word) in a grammatical category, such as gender, number, case, or person. 

  • To yield assent to; to approve. 

  • To resemble; to coincide; to correspond. 

buy into

verb
  • To believe; to accept a craze or fad as valid. 

  • To buy stocks or shares of (a business). 

How often have the words agree and buy into occurred in a corpus of books? (source: Google Ngram Viewer )