That's a reasonable first approximation. But let's say two studio's both like the script and only one wins the bidding war. What stops the other studio from farming out the 'high concept' to someone else to write an also ran. As far as I can see nothing, so the value of a script is basically limited by what it costs someone else to create the same basic concept. Toss in the fact that scripts tend to mutate after production anyway and the 'we can always steal it' must be at the back of all negotiations.
Which is oddly similar to the buy vs. pirate internal debate I have seen several people go though on hard to find content.
EX: Underworld did not use any of white wolf's IP. There was a negotiation, but in the end the studio 'went in another direction' that just happened to look the same as if they had used their IP.
"the 'we can always steal it' must be at the back of all negotiations."
With all due respect, this is a big and mostly incorrect leap. If intellectual theft happens in Hollywood, it's typically an exception and not, as you're implying, a general rule. It certainly isn't something studio execs keep in the back of their minds as part of the development process. That's outlandish.
Most studios are extremely frightened of litigation over this very topic. So much so, that when I worked at a TV studio buying scripts, I was not even allowed to open any unsolicited material sent my way. If someone sent me a package, and I didn't recognize the return address, I sent it off to legal, to be returned unopened. About 99% of the scripts and ideas I was pitched came about in meetings with agencies and/or producers, who were also bringing the same material to all of my competitors.
The behaviors you're ascribing to studios seem to be occurring at the producer level. There's a high variance of ethical and professional conduct among production companies and producers, in as much as they're not public companies like the big studios and networks are. They don't have a set rulebook. Most of the more established producers are unlikely to steal material, because it's a terrible long-term business strategy (a producer's reputation is his meal ticket). That said, are there some shady folks on the fringes of the business? Yes. Anyone who says otherwise is being willfully naive. But the idea that people at studios actually calculate theft into their buying or development strategies is patently absurd.
"What stops the other studio from farming out the 'high concept' to someone else to write an also ran."
Three things stopped me from doing that, and stopped my peers from doing that:
1) Personal and professional integrity.
2) Relationships and reputation. (Hollywood is an extremely relationship-driven business. As a development executive, I was worth approximately nothing; what made me relevant to my employers was my network of writers, agents, and producers I could bring to bear for projects. Burning any of these people would have been career suicide).
However, despite following the case closely at the time, I've never heard about any negotiations between White Wolf and Sony at any stage of the film's development. On the contrary, emails from within White Wolf indicate they were completely unaware of the film until the first trailer was released. Do you have a source for your claim that there were negotiations?
To answer your question: nothing stops a studio from piggybacking on someone else's concept, and nothing should. The Asylum's entire business model is based on it (though they also engage in the somewhat unethical practice of copying names, when they can). White Wolf has no claim to the basic ideas underpinning the World of Darkness. There's nothing unique or innovative there.
The same thing applies to The Vampire Diaries (books and TV show), Twilight (books and film), True Blood (books and TV show), and so on, of course.
Which is oddly similar to the buy vs. pirate internal debate I have seen several people go though on hard to find content.
EX: Underworld did not use any of white wolf's IP. There was a negotiation, but in the end the studio 'went in another direction' that just happened to look the same as if they had used their IP.