Toby Young: Is Art Buchwald the man behind Harrison Ford's success?

The news that Harrison Ford is Hollywood's highest-earning actor may come as a surprise to some. After all, isn't he a bit of a has-been? His last film, Crossing Over, grossed less than $500,000 at the US box office. Yet according to Forbes, the 66-year-old action star earned nearly $65m in the 12 months between June 2008 and 2009. How did he manage it?

The answer is that he was a profit participant in Indiana Jones and the Crystal Skull, one of the most successful films of 2008. Not only that, but he was entitled to a share of the "gross" profits, rather than the "net" – by common consent, the most important distinction in the movie business. "I've been in this business for 20 years and there are two things I've learnt," says the independent producer to the studio executive in Speed the Plow, David Mamet's satire about Hollywood. "The first is there's no such thing as the net. I forget the second."

The principle that "there's no such thing as the net" was definitively established in a court case known as Buchwald v Paramount. In that lawsuit, the writer Art Buchwald sued Paramount Pictures, arguing that Coming to America, a 1988 film starring Eddie Murphy, was based on an original idea he'd submitted to the studio several years earlier. According to his contract with Paramount, Buchwald was entitled to a percentage of the "net" profits. As part of its defence, Paramount argued that that, due to development and marketing spend, that figure was zero, in spite of the fact that Coming to America grossed $350m.

The judge ruled in favour of Buchwald, but even though he allowed for the fact that Paramount's definition of the "net" was "unconscionable", he only awarded the plaintiff $150,000 in damages.

Since the lawsuit, which lasted seven years, cost over $3m, Buchwald was seriously out of pocket, but he claimed a "moral victory" nonetheless – and he was right. Thanks to the publicity the case attracted, no one entering into a contract with a Hollywood studio who possesses any negotiating power will ever again allow themselves to be fobbed off with a percentage of the "net".

When Harrison Ford cashes that cheque for $65m, he should say a silent prayer for Art Buchwald.