I agree that some wealthy and eccentric people buy ridiculously expensive items because they can. In the case of buying rocks from Nordstrom for $85 it only helps to prove this point. Unless the rocks are rare or posses some quality that other rocks do not, there is no reason they should cost that much. But again, some wealthy and eccentric people will buy anything because they can.
For the rich, it is important to buy something just to buy something. They do not care what the purpose is of the thing that they are buying. They just want to be able to brag to their friends that they bought it. They think there is something to be said for acquiring something, even if it isn't anything special.
One should never lump a large group of people into a single, simple descriptor. However, on the whole, it seems that when one has more and more disposable income, they become less thoughtful on what they spend it on. Any of us can get caught up in commercials and be sold on items we do not need, especial in the moment of an impulse buy, but when one has enough income they may lack the filter to say no to the item.
The leather wrapped stone sold by Nordstrom is just the latest example of the old saying, "There's a sucker born every minute." The over-the-top description worked for enough people. The curious $85. offering and the smaller $65. version are both listed as sold out currently. The appearance that it is an in-demand item adds to its popularity.