<prompt> Human: Theres an article 1 that says that on 300K-AUD australian dollar mortgage at a rate of 4.31 for 30 years, you can save 71K-AUD - if you give up your daily cup of coffee5-AUD. Does it make sense ? how ? and what are the caveats?1Assistant: Yes it makes sense. The caveat is that you dont have that cup of coffee in the morning. However, you can find something else to replace to make up the difference if youd rather. Bring a sack lunch, stop smoking cigarettes, stop buying water bottles, bike to work, anything thatll save you a few bucks that you can throw towards mortgage instead.Heres an excess payment calculator.Human: thanks. great answer. and i agree that saving in general is a great strategy in life. But i wrote the data inside the calculator, with money saved on coffeeadditional principle payment equals 120month. and the savings amount i get is 37K over 30 years. which is very different from the article. Is there something wrong with the caluclation ? or is the original articleb is just bullshit ?  <response>: your calculation is incorrect- you are forgetting to add interest savings into it. When you pay off your mortgage early you save a ton of interest by paying down the principal much faster. 