Few years back, when we decided to sell the house, we had a new fence put up.  The old fence was 25 years old and falling apart.  Our lot is an acre so it was a big expense.  It came up in conversation last week, my wife mentioning it cost $30k.  No, I replied it was more like $10k.  My wife looked it up and the cost was actually $20k.  We were both right, on average.