How are prices determined in a monopoly?

Let's say I have a monopoly on some good X. Nobody else sells X but me in the entire world. There are no substitutes or alternatives. While I could set the price of X at a million dollars, people will just decide they don't need X, even if there's no alternative to it. X could be something like potato chips, cars, a life-saving drug, etc. I'm curious how you actually go about optimizing the price for different amounts of demand.