A Penny For Your Thoughts

If you can read minds then you would never have to ask the question a penny for your thoughts.  It is a cute way to ask someone what is on their mind.  A guy asks a woman, "Will you marry me?"  He does not get a reply and then immediately follows up with the question a penny for your thoughts.  Sounds kinda corny.  With inflation should we be instead asking a quarter for your thoughts.  What can you really get for a penny these days?  I was even hearing talks about the government getting rid of a penny.  So far that has been a big rumor because I heard that over 10 years ago.  Actually lots of people will not even pick up a penny on the ground and especially one on tails meaning bad luck.  How about if someone comes up to you asking to borrow a hundred dollars and then says a penny for your thoughts.  Is it appropriate to say the saying a penny for your thoughts when someone is getting engaged or borrowing money?  Does the saying really work?  I might as well carry a penny around just in case someone really wants me to give them a penny for their thoughts.