Bonhams' poster specialist, Adrian Cowdry of the Cineart Gallery, says the price rises have been phenomenal. "I bought Goldfinger for £6 in 1980 and now it's worth around £3,500. In 1970, a big collector in the US was the first person to pay a $1,000 for a poster, from the 1931 Frankenstein movie, and now it's worth £150,000 or more."
The market has risen so quickly that some classics may be out of reach for new investors. "Certain titles, such as King Kong, Gone with the Wind and Thirties horror titles have probably hit a ceiling because many people entering the market now are a long way off being able to pay £200,000 to £300,000," says Christie's poster specialist Sarah Hodgson. "Most collectors are very much under the £10,000 bracket, but some of these people may start spending more."
Prices are affected by remakes and reissues, or trends. "Titles lose favour for a while and then come back in," Cowdry says. "Others, like Breakfast at Tiffany's and the first six Bond films, are always up there."
Hitchcock films fall into the first group, and Laurel & Hardy or Charlie Chaplin films are always popular. "The really big money is in Universal Monster films, the 1931 Dracula with Bella Lugosi, the 1931 Frankenstein with Boris Karloff and the 1935 Bride of Frankenstein ," Cowdry says.
"There are also going to be icons such as Audrey Hepburn but younger people are interested in movies such as Scream, Kill Bill or Alien. Tarantino has picked up big time with Kill Bill; there's a Japanese version that's about £500.
"Generally speaking, anything from the Sixties backwards is popular, but there are a few titles from the Seventies and Eighties people are picking up on - Jaws, the Indiana Jones films, Ferris Bueller's Day Off, Ghost Busters and The Blues Brothers. A good version of Jaws would cost £300 to £400, while the Indiana Jones posters are up to £300."
Bonhams' group head of collectables Jon Badeley thinks even contemporary movie memorabilia are worth a try. "It is very much focused on modern culture," Badeley says. "In 20 to 30 years' time, people will consider the cult movies of today as avidly collectable."
Some areas of the market have yet to be explored. Christie's is to hold a specialist film-poster sale called Exploitation. "It covers, sex, drugs, teenage rebellion and the like, mostly from the Sixties," says Hodgson. "It's a bit of an unknown quantity, but we've had a huge amount of interest."
Bollywood films have also begun to generate interest, and experts expect this to be a growing trend. "These films have a great following and there is some amazing artwork from the Bollywood era," Cowdry says. "Some Bollywood posters are going for £1,000 or more, but as with any area of collecting, you need to do your research. It's a prolific movie industry with a lot of posters produced, so buy the rarer ones and the classics."
If you're looking for the next big thing, consider lobby cards from the US and front-of-house stills from the UK. These have been almost entirely phased out, but older examples are popular. A lobby card from Casablanca will sell for £1,500 to £10,000.
Bonhams: 020-7447 7447 (next sale 16 November)
Christie's: 020-7839 9060 (Exploitation sale on 8 December)
Cineart Gallery: 020-7384 0728; www.cineartgallery.com