The snob effect is a phenomenon observable with certain products and services among certain groups of consumers. For example, when a new night club strictly limits who can get in, its exclusivity will have a strong appeal to certain individuals, but if the same night club were to suddenly throw its doors open to the general public, the night club would be completely unappealing to the same individuals.
In microeconomics, the snob effect is a phenomenon referring to the situation where the demand for a certain good by individuals of a higher income level is inversely related to the demand for the good by individuals of a lower income level. This situation is derived by the desire to own unusual, expensive or unique goods. These goods usually have a high economic value, but low practical value. The less of an item available, the higher its snob value. Examples of such items with general snob value are rare works of art, designer clothing, and sports cars. Ultimately, wealthy consumers can be lured by superficial factors such as rarity, celebrity representation and brand prestige. We can also talk about veblen goods to define those kind of goods. (T. Veblen)
Sources : Dacko, S. (2007) & Wikipédia