It’s official: 3 is the new 2. Criticised for rehashing old plots and hiring over-familiar faces, Hollywood has finally produced a roster of summer movies that aren’t all sequels. But there’s a catch: most of the films are “threequels” instead.

What Hollywood might lack in originality it hopes to make up for in, well, cash. And so far, the dollar signs have been showing a much-welcome early bloom. The first threequel of the summer is Spider-Man 3, which enjoyed a record-breaking $30 million (£15 million) “soft” opening on Tuesday.

That easily beat the first-day takings of the previous two Spider-Man films, which made $1.6 billion for Sony Pictures – not including the lucrative side-lines of DVD sales, merchandise and pay-per-view fees. After Spider-Man 3 will come Shrek the Third, Pirates of the Caribbean: At World’s End, Ocean’s Thirteen (the third in the Las Vegas crime/caper series, after Ocean’s Eleven and Ocean’s Twelve), The Bourne Ultimatum, and the less keenly awaited Rush Hour 3.

Deep inside the studio lots of Burbank, Hollywood and Culver City, there is already whispered talk of a magic number: $10 billion. That would mark a record for domestic American box-office takings in a single year, beating the $9.54 billion taken three years ago.

Is 2007 a good enough year to make the leap? Jeff Bock, a box-office analyst for Exhibitor Relations, put it bluntly: “We’ve never seen a summer like this.” But the stakes are also high: Spider-Man 3 alone cost $250 million to make, not including marketing and distribution costs. And audiences often lose interest in a franchise by the time it gets beyond the second installment – as they did with The Matrix Revolutions, and, years earlier, Back to the Future Part III.

Last year, it was a remake of Superman that provided one of the biggest financial let-downs. But the success of long-running TV serials such as Lost and The Sopranos has convinced studio executives that cinemagoers have an appetite for more, as long as the quality remains high. The TV show 24 was into its sixth season before viewers began to get bored.

Some movie franchises already seem to have infinite appeal: Harry Potter and the Order of the Phoenix is a sequel of a sequel of sequel. The Harry Potter movies have been going for so long that their star, Daniel Radcliffe, has grown from a 12-year-old to an 18-year-old who admires Gary Oldman, appears naked on stage and listens to the Sex Pistols.

Studio executives – and the people whose careers depend on them, including LA real estate agents, Porsche dealers, and restaurateurs – believe that they are long overdue a good year. The infamous box office slump of 2005 was particularly miserable for the studios, and the improved performance last year – when 607 movies were made, 1.45 billion tickets sold in the US and revenues were up 5.5 per cent – was overshadowed by production costs.

When Paramount Pictures ended its contract with Tom Cruise, many believed that it was the beginning of a new, leaner, and more troubled era for Hollywood. Movie stars, it was declared, would never again earn $20 million per picture. But such worries appear to have passed already .

“Given [the movie lineup] of 2007, my educated guess is that it will be bigger than 2006,” said Dan Glickman, of the Motion Picture Association of America. “The last time we had so many sequels, in 2002 – it was a pretty big year.”

As if Hollywood is trying to convince itself that business is looking up, monster-sized billboards have been erected along Sunset Boulevard advertising Shrek the Third, boasting: “The Wait is Ogre”.

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