This is a very interesting question first of all I would like to distinguish between the type of goods which you mentioned above since there are subtleties between them which are key to answering your question.
First of all we have Veblen and Giffen goods which both share the feature in that when their price increases so does demand. An example of a Veblen good is a Louis Vuitton handbag since the good becomes more attractive as its prices increase. On ther other hand we have Giffen goods which are not luxury goods but their demand increases with price for example if we have a very poor economy in which families consume only bread and meat, when the price of bread increases they no longer buy meat and end up buying more bread.
The above paragraph shows us that the utility of this two type of goods not only depends on the quality of the good but also on the price and as you said when finding this type of equlibrium walrasian equilibrium assumptions violated
Now we have the other type of goods which are Bandwagon and Snobb-effect goods in which the key difference between the two types of goods above (Veblen and Giffen) is that these goods depend on other peoples consumption and not on the prices. An example of a bandwagon good is a buying a stock in a bull market because people tend to buy a stock just because others are cosuming it. Snobb effects are the exact opposite since these are goods which are unique due to to that few indivuduals have it like expensive jewley.
With this two types of goods utilities depend on other peoples consumption, an example which you could try to solve is problem 1.2 titled inefficient markets and you can easily interpet that problem as a “snobb effect” since agents utilities are diminished as the other consumes more of a good