Frank Williams says there is no amount of money that could get Nico Rosberg released from his contract early.
The German driver, who joined Williams for his debut season in 2006, has a contract with the British squad until the end of 2009.
Williams says Rosberg is playing a key role in the team's work to return to the top end of the field, and that there's no chance that he will leave early.
"Nico is fundamental for our growth, we have an agreement with him until the end of 2009," Williams told Autosprint magazine.
"Maybe someone will want to take him away for 50 million dollars, but contracts are contracts. And this year, our financial situation is a lot more solid than in 2007."
Williams added that his team had the chance to sign Robert Kubica before the Pole secured a deal to race in Formula One with BMW Sauber.
"Kubica is really good and I'm ashamed to say that three years ago he was available, we could have hired him, but we never fully considered it," he added.
"Our priority was Nico, he's really magic. We all know Lewis... Nelson Jr? I don't know."