<prompt> Human: Recently I started selling some of my stuff as I need to supplement my income in order to cover my bills. One problem I am having is dealing with people who haggle on prices. I know that what I paid are sunk costs. But part of me is having difficulty letting things go at 50 off and less. Any advice on how I can deal with this?Thanks in advance!  <response>: Look at the amortized price. I practice photography. Lenses hold value. Camera bodies, which are updated every 1-2 years do not. The camera I buy today for 2000 will probably sell used next year for 1500. I dont see it as losing 500. Instead, I rented a camera for 500 for one year. By comparison, I could have paid that much to rent a camera for one week!tl;dr Compare the sunk cost over time with the cost of renting equivalent property for the same time period. 