Cady Noland - Oozewald, 1989
The Image is Oozewald, an installation sculpture by Cady Noland created in 1989. Cady is considered to be an influential member of the art world in the late 1980s and early 1990s. She then promptly removed herself from the art market. This move has made her work scarce and has left a place for her work to grow in value as the demand can potentially exceed the supply which has ceased to increase. An article on the political significance on her work highlights the importance of her American political commentary and the minimalistic movement.
In November of this past year, her above sculpture sold for more than double the high estimate of the action at Sotheby's in New York. The estimated low of $2, high $3, and selling price with buyer's premium of just over $6.5 million. This is a prime example of the premium prices being demanded in the auction house market by established collectors, dealers, and advisors. The market is in a bubble. Prices are soaring for contemporary works, and these works are being traded by powerful players for extreme monetary gain.
There are some collectors who do not resell the work they buy, but prefer to hold onto it as selling can be taboo. However, this behavior is mostly indicative of the primary market where works by young new artists are sold for the first time. In the auction houses, with the rare exception of incidences like Hirst's selling of the Pharmacy works, the pieces going up for sale are on the secondary market and are thus thought of more as an investment opportunity than a sentimental buy for people looking to enrich their art portfolios. 
Sotheby's Auction House
Until recently the art of living artists was sold privately, with only work by masters on the public radar. The prices of the privately sold pieces were thus not necessarily common knowledge. With the recent trend in the auction houses of selling contemporary art, though usually no fresher than 2 years old, an artist can be branded by the auction house and this branding will inevitably raise the price of their work. People publicly see the new artist among their respected and established peers and ultimately associate that young artist to be of the same caliber (and price range). Yet when an artist like Cady Noland stops producing art work, it is like she has died and the supply of new work by her has been cut off from the market. Therefore when her work comes to the lot, there is the palpable tension created by scarcity and the "need to buy the work now".
Where the market used to thrive on the work of the great masters, a scarcity effect has limited their sales as well. Since the masters are long gone, and museums or other institutions are starting to collect their pieces, it is rarer and rarer to see them offered up at auction, as many people are unwilling to let them go. When they do happen to be released, unprecedented bidding wars have broken out causing record high prices and a sense of urgency on the part of the buying party. This being true, the market is moving towards offering more and more young artists because they are "running out" of work to put up, and being forced into a more contemporary market within the houses. Also, because the masters are being held and the contemporary works are being traded, many financially savvy collectors are seeing the art market as a mode for investment with quick, steep returns when their taste is right (or their advisors are good). Art investing is a more recently pervading fad. Before where the only acceptable reasons to sell in the art world were the 3 Ds, a 4th D for dealers has been added where many are selling for money.