Take Pink Floyd, for example, reforming after 20 years to play Live 8. MEM Music and Cinema Memorabilia is selling a poster from one of the band's first gigs, in The Barn, Abergavenny, for £3,000.
Until now, the pop memorabilia market has been heavily dominated by the Beatles and other bands of the Sixties. "Almost half our sale is Beatles memorabilia, but we also sell the Stones, Hendrix, Dylan and that sort of thing," says Sarah Hodgson, Christie's head of popular entertainment. "Most of the big band artists from the Sixties are collected because not only was there a huge shift in taste from the Fifties to the Sixties, but the music also reflected the social and political trends of the day."
Success in the charts is not necessarily a ticket to the auction rooms, however, as Stephen Maycock, a consultant specialist in rock 'n' roll memorabilia at Bonhams, explains. "It has to be down to what real impact that band or artist has made on music," he says. "It's all very well selling records, but have they changed the course of music and done something new?"
For example, you are unlikely to get a Cliff Richard autograph in a Bonhams auction,even though he is the UK's biggest-selling artist, partly because there is too much supply and partly because he's not seen as ground-breaking.
Collecting is heavily dominated by people who want to buy back items from their childhoods. Now, with the thirtysomethings and fortysomethings coming into the marketplace, items related to artists from the Seventies and Eighties is likely to rise in value.
"Looking at the Seventies, the names are Yes, Queen, Marc Bolan, Led Zeppelin, Elton John and the like," says Maycock. "Towards the late Seventies, you get the Sex Pistols, who are like the Beatles in the Sixties, and they completely dominate the punk era. In the Eighties, in times past, Michael Jackson would have been up there, but his pulling power in the memorabilia market has all but disappeared."
Maycock says Madonna has a following because she has been so clever in reinventing herself. Christie's recently sold an old copy of Harper's Bazaar, signed by the artist, for £500. It has also sold a signed Oasis album for more than £300. "At the height of Oasis's fame' memorabilia was doing very well, but as their career has made less of an impact, so did the memorabilia," he says.
Mike Bloomfield, of MEM, thinks indie bands such as Oasis, Blur and Happy Mondays could become more collectable in the future. "I'm currently handling some material from the band James, who came out of Manchester in the Nineties – it's only 10 or 12 years' old but it already has a cachet," he says. "Their vinyl has been quite collectable but paper memorabilia, if you can get hold of it, is going to be quite a good investment."
Indie artists who have worked hard to create their own style are more likely to have memorabilia longevity compared with the "manufactured" bands. The Spice Girls, who were collectable during their career, are a good example: their popularity seems to have evaporated.
Items from times before artists were famous tend to rise fastest in value, and even with bands such as the Rolling Stones their early material is the most sought after. Christie's has sold an early Stones poster for more than £3,000, for instance.
One problem is that in the past 15 to 20 years, big stadium bands have been making money through merchandising. This material has been available in large quantities, so it won't make money.
Buying items owned by an artist is a collector's ultimate aim, but Bloomfield thinks the rest of the market has shifted a little.
"It's been dominated by autographs and concert memorabilia, but the artwork for the albums is quite a new area which is rising in importance," he says. "Even the record-collecting market is much smaller than it was 20 years ago – then you had a lot of people who were collecting records, but now it's a much smaller, elite group who want the rare records in excellent condition."
There's no doubt that iconic artists such as the Beatles and the Sex Pistols will retain their popularity. For more affordable investments, if you can spot ground-breaking artists and buy their early material, you could build up a nice nest egg.
But be careful where you buy from – fraudsters are common. In one recent case, an internet dealer advertised a Billy Fury Memorial Concert poster for sale – despite the very obvious memorial tag, the poster was supposedly signed by Billy Fury.