Desire Ability to pay Willingness to pay It is not enough to merely want or desire an item. One must show the ability to pay and then the willingness to pay. If all three conditions are not me then the demand is not real. This, by the way, is the purpose of advertising. While many may want a product it is quite another to be willing to pay.
Advertising attempts to move a consumer from mere want to action.
These day even condition two may not stand in the way of a consumer. With the advent of credit cards we are able to purchase products without the current ability to pay. Many stores and car dealers even offer on the spot credit though the interest rate may be quite high. Some factors include consumer income, consumer tastes the prices of related products like substitutes for that product of items that may complement that product. Marginal utility - extra satisfaction a consumer gets by purchasing one more unit of a product.