not quite true, some things create an entirely new market which may or may not find demand depending on the market.
fashionable clothing for example does not appeal to the buyer through utility, durability or low cost, it sells solely based on the whim of the buyer, and their desire to be foppish. trousers with holes in them, jeans with sparkles, glitter and rhinestones, or shirts that are 6 sizes to big are in no way functional. they are entirely based on the fancy of popinjays.
these senseless garments do not detract from the sales of real clothing, as the clowns and minstrel performers who wear them would be disinterested in the clothing worn by people who work for a living.
luxury goods and sumptuary products are separate from the laws of supply and demand, in that there is no "Demand" only desire. and foolish desire at that.
or looked at through another angle, lowriders do not detract from the sales of normal automobile parts, they simply create a market for shitty hydraulics kits, sparkly paint, and tiny steering wheels. those who indulge in these flights of fancy are not creating a demand for chopped suspensions and banged up mufflers (if equipped) they simply are simply creating a market by which fools can be separated from their money in exchange for whistle tips and faux fur dashboard covers.
if nobody were foolish, foppish or stupid, there would be no demand for laceless sneakers 5 sizes too big (we used to cal them slippers), whistle tips, or shamwows. therefore there would be no producers of such products, and the world would be a little less funny, and a little less colourful.