Their grey faces stare blankly out, girls with pigtails, men in collarless shirts - images from a lost world, a regimented China that died with Chairman Mao. But Zhang Xiaogang's oil-painting series Bloodline, inspired by family portraits from the Mao era, is very much part of today's commercial China. An average-size canvas sells for a million dollars, and his biggest - owned by a Chinese collector - has been valued at $5m. He has outsold Damien Hirst and Jeff Koons; according to Artprice.com, sales of Zhang paintings at auction in 2006 raked in $23.7m, putting him second in its 100 top-selling contemporary artists. A few years back, no Chinese artists featured in the Artprice top 100. Now there are 25. Prices have rocketed. Last year, auction sales for Asian - mainly Chinese - art at Christie's and Sotheby's totalled $190m, an eightfold increase in two years.
"When we started we never thought we would sell our work for money," says Feng Zhengjie, who recently sold one of his characteristic huge pink and green Warholesque women's faces to Maurice Saatchi. "We lived through hard times. This is all new. It's way beyond our expectations."
Feng was a high-school and college art teacher in Sichuan before he came to Beijing in 1995. His contemporaries are less overtly political than the Tiananmen generation, which had struggled with the authorities to exhibit angry representations of state violence and repression. Feng's early paintings were inspired by 1930s Shanghai posters. In his more recent work, he has taken the red and green of traditional Chinese New Year paintings, he says, and made the colours more acid, a representation of the flashy, commercial nature of modern China. But he participates in the commercialism he portrays, recently adding 2008 Beijing Olympic logos to three of his women's faces as a commission for Adidas.
The centre of Beijing's art world is Dashanzi, a reconditioned armaments factory, now featuring 400 galleries, cafés and art shops. Although some of the top-selling artists can be found exhibiting here, it's more Camden Town than the Courtauld, attracting foreign tourists and the Chinese middle class as well as collectors.
A rising tide lifts all boats, so artists of questionable quality - to say the least - are commanding ever higher prices. There are endless Maos by artists who hadn't been born when Mao died.
"It's as if there aren't enough Rembrandts to fulfil the demand, so his brother's having a go, and all his friends," says Colin Chinnery of the Ullens Centre for the Arts, the first non-profit organisation in Dashanzi. "Frankly, most of it is pretty poor quality."
At the moment, many Chinese artists appear to be reproducing the same painting again and again with only minor variations - and finding that each new version fetches an even higher price. Chinnery hopes that a non-profit exhibition space will provide artists with an alternative form of recognition to commercial success, so that the market is not the only arbiter of taste.
Not surprisingly, gallery owners and dealers have a different take. "I don't believe this is a bubble or that Chinese art is overpriced," says Julia Cameron, who established the Chinese Contemporary gallery in London a decade ago. "I think the famous Chinese artists are finding their level alongside the British, Americans and others. They're great - they have a lot to say."
Guan Yi wanders in between two giant fish suspended from the ceiling of his huge warehouse. When he started to collect Chinese contemporary art six years ago, using his family fortune from the chemical machinery business, few people were interested in his eccentric array: a life-size jeep with a tree growing out of the top, made of stone; a replica of the US spy plane downed over Hainan Island in 2001; a large Buddhist prayer wheel deconstructed to look like a spear and shield. Now Wan gets local business people and international art curators calling every day. His collection has quintupled in value.
"But we don't know the real value yet," he says. "It's too early to say. There's no history, no context for Chinese art, and now people are buying like stocks and shares, not necessarily because it's good."
Life mimics art. Artists whose main subject matter is the commercialism of modern China are becoming as wealthy as any other successful business people. As the days of protest fade, 18 years after Tiananmen, some see Chinese artists becoming engulfed by their subject matter.
"It would be terrible if the artists became part of the money-worshipping society we see today," says Wan. "Their role should be to criticise and comment on society. If not, they will be no different from the coal-mine bosses who buy more and more mansions because they don't know what to do with their cash."
Lindsey Hilsum is China correspondent for Channel 4 News