There are other factors at play also. Redbox is actually $1 per day. Keep it longer, pay more, all the way up-to the price of the DVD, in which case you just keep it. And probably more significantly, they can only hold a very limited supply: someone takes out that new release, it's out, and your options are then go online or another box hoping to find it, guess when the person that got it out will return it, opt for another movie, or, pay a higher price with another vendor to avoid these pitfalls.