Like another, later series that tore apart, satirised, reduced and then reassembled Velasquez's Las Meninas, these works were intended to be seen together. I saw Picasso's displayed alongside their classical inspiration in Paris in 2008, and it was unforgettable. Picasso's dealer, Daniel-Henry Kahnweiler, sold the Women of Algiers series in its entirety in 1956 to American collectors Victor and Sally Ganz, who paid $US212,500 (about $US1.9 million today). They soon realised they couldn't afford it and sold all but five of the paintings. That was like breaking up a family, but Picasso was still painting and it probably didn't seem like much of a crime. Yet, reuniting the series became a daunting task. In 2009, the Louvre held an exhibition devoted to the Femmes d'Alger project, but just four of the large compositions were displayed, along with several preparatory studies. The Ganz collection was auctioned in 1997, netting $US207 million. Version O, originally acquired for $US26,632, brought $US31.9 million. The auction provided such spectacular returns on the original Ganz investment that it became the subject of an academic paper by William Landes of the University of Chicago.

He wrote of the Ganzes: "They didn't hit the jackpot overnight. Rather, they spent a good deal of time and effort searching and acquiring art over many years. And like long-term investors in general, they had enough confidence in their purchases that they followed a 'buy and hold' strategy." It was probably wrong to describe the collectors' life work in investment terms. The couple loved their paintings, hanging them around the house and loaning them to museums to be exhibited. It was a passion born of deep knowledge and a feeling for true genius. The 1997 auction only took place 10 years after Victor Ganz died. His children struggled to pay inheritance taxes. A London art dealer, Libby Howie, acquired Version O at that auction. As it turns out, he was acting on behalf of a client, the anonymous person who sold the painting on Monday. This was probably already a rather dispassionate investment. The seller spent serious money and more than quintupled the outlay in 18 years. Nonetheless, the painting still sometimes saw the light of day: It was at the Louvre exhibition, for example. Howie was listed as the loaner. Nothing is known about the new buyer. Art critic Jerry Saltz, who went to see Version O at Christie's auction house before the sale, said goodbye to it with a grandiose description that betrayed something of a lover's obsession, writing: "I knew almost everything I saw might not be seen again in public."

Today's collectors often keep their art in freeport​ warehouses, where the works are seen only by their owners and prospective buyers. To these people, art is an alternative to other markets, such as bonds, equities and real estate. Deloitte's Art and Finance Report shows post-war and contemporary art provided an annual return of 10.5 per cent between 2003 and 2013 , compared with 7.4 per cent for the Standard & Poor's 500 Index. In the past two years, judging by all the auction records that culminated in Monday's sale of Version O, the returns have probably been even better, especially on top works. In 2011, the Berggruen Museum, owned by the city of Berlin, bought Version L for $US21.3 million, and it has drawn crowds. Even Picasso's granddaughter showed up to look at it. However, in the current art market, an institution such as the Berggruen cannot hope to assemble the whole Picasso series. It's probably even beyond the means of the tremendously wealthy Nahmad family, which has some of the Femmes d'Alger paintings.

No matter how much auctioneers, dealers, art owners and fashionable painters may love this market, it is an abomination. Governments, which routinely meddle in saner, healthier markets, must step in to ensure that masterpieces can be seen and admired by the public. Picasso, an avowed leftist, certainly meant for his work to be widely seen, not just traded. "What do you think an artist is?" he said. "He is a political being, constantly aware of the heart-breaking, passionate, or delightful things that happen in the world, shaping himself completely in their image. Painting is not done to decorate apartments. It is an instrument of war." With the sale of Version O to an unknown individual for an indecent pile of money, Picasso lost an important battle in that war. Leonid Bershidsky, a Bloomberg View contributor, is a Berlin-based writer.