About estimations

gistfile1.txt

P = programmer; NP = non-programmer

  NP: How long will it take?
  P:  It'll take as long as it takes.
  NP: I don't understand. What does that mean?
  P:  When you tell me that the product is finished, it's done.
  NP: You mean you can't estimate how long it'll take?
  P:  I can't estimate when you'll decide that it is done, therefore an
      accurate prediction is impossible.  From experience I know that a
      project like this can take from three to nine months.  A lot 
      depends on you, the choices you make and how well you communicate 
      them to me.  A lot also depends on how many times you change your
      mind during the process and how many times you change the
      specifications during the job.  Major changes can even cause the
      project to be scrapped and start over.  Rest assured that I will
      not be the one slowing this down.
  NP: How much will it cost?
  P:  It will cost as much as it costs.
  NP: I don't understand.  What does that mean?
  P:  You just learned some programming!  
      Go back to your first question and re-read the entire thing.  
      This is called an endless loop.

Source: http://news.ycombinator.com/item?id=3795513