This MIT symposium. In the first session, Jerry Hausman winds up talking about a paper he did on the demand for energy-efficient air conditioners. For what it's worth, I was the research assistant for that paper. He found that consumers buying durable goods act as if they have very high discount rates. He says in the talk that this finding led him to advise cell phone companies to offer very low initial prices for phones and make up the loss with higher monthly rates.