It is the classic demand-supply curve, the cornerstone of Economics 101, in operation.

In Bollywood, the stakes have become tempting enough to draw in increasing numbers of investors, all looking to strike the mother lode at the box office.

Against that, the majority of hits are still star-driven, with the few story-driven sleeper hits being seen as the exception, not the norm.

And there is a desperate shortage of saleable stars, with the same six or seven names headlining the majority of the movies being made.

Hence, star salaries are going sky-high, reports the Financial Times.

FT quotes Siddharth Roy Kapur, COO of UTV Motion Pictures, as saying 'The number of stars in the industry hasn't increased in the same manner as the funds available for film production have increased. So it's quite natural in a market like that the costs will go up.'

Indian broadcaster NDTV, which has plans to get into the film-production business, agrees. Sameer Nair, head of NDTV's newly formed entertainment channel, calls it a "general scarcity problem." And there is no solution in sight.

In the normal course, such a situation would have merely impacted, negatively, on the number of films being made -- but this scarcity coincides with the problem of plenty as far as money is concerned.

In the previous 12 months alone, reports FT, as many as three Indian film companies have listed on London's [Images] Alternative Investment Market, while others are tapping the domestic stock market. Elsewhere, some companies have tied up with Hollywood production houses.

These initiatives have helped raise funds in the millions of dollars, which are meant to be invested in films. Producers need stars to headline these films, and since they can increasingly afford to pay extravagant sums to sign up marquee headliners, the stars have started cashing in.

Top stars are currently earning in excess of Rs 100 million per film, which is double, or even triple, what stars made at the turn of the century. And star salaries are going further up, not down.

The solution, say some, is to make the switch from star-driven to story-driven -- or, as they say in the trade, 'concept' -- films.

'Everyone has shown up with a truckload of cash to make bigger and better movies, but they have got to move on from relying on these same few movie stars,' FT quotes Nair, who prior to joining NDTV was the CEO of Rupert Murdoch's Star Entertainment India channel.

Studios aren't prepared to switch formulas yet. For now, they prefer to lock top stars into multi-film contracts, with Priyanka Chopra, signed on by UTV for three films over four years, being merely the latest example.