Why is Gerhard Richter worth £21 million? Richter's late, abstract works are particularly sought after because of their broad appeal: colourful abstracts which can fit into any interior, cannot offend anyone (unlike some of his tougher earlier works which deal with death or politics) and are recognizable trophies which give the owner immense bragging rights. Cynics point out that, as well, they are domestically sized, so ideal for a luxury apartment - or yacht. And, as Richter is now aged 80, the market recognises that he will not be painting forever. Add to this a career carefully managed by long-term American dealer Marian Goodman, and by the artist himself, who maintains a detailed website enabling prospective buyers to identify all his work and its sale history - something that has particular appeal to those with investment interest. Finally, his market is global: buyers come from all over, from South Korea or Brazil as well as from the US, which has a solid appetite for his work. The Russian billionaire Roman Abramovich has another squeegee work, bought for $15.2m in 2008, and there is reason to think that this week's buyer was also from Russia.