gross profit vs payback

gross profit

noun
  • the difference between net sales and the cost of goods sold 

payback

noun
  • A return on investment. 

  • An act of revenge. 

  • A benefit, reward, a form of recompense. 

  • A refund; reimbursement. 

How often have the words gross profit and payback occurred in a corpus of books? (source: Google Ngram Viewer )