Saud Arabia's crown prince may be the mysterious buyer of a rare Leonardo da Vinci painting, a report in the Wall Street Journal suggested Thursday.

According to the article, Prince Mohammed bin Salman, known to be a fan of the arts, used a proxy to buy the masterpiece. However, the high profile purchase, with a price tag of nearly half a billion dollars, comes at a time when the Saudi prince is leading a massive corruption crackdown on his country's wealthy elite, CBS News correspondent Holly Williams reports.

Despite the painting's hefty fee, it was pocket change compared to the staggering misuse of public funds revealed by Economy Minister Mohammed al Tuwaijri, who told CBS News that 20 billion dollars a year has been lost to corruption.

"It's negligence. It's overspending in some projects, spending on unnecessary projects, and so on and so forth," Tuwaijri told CBS News.

Al Tuwaijri took over as Saudi Arabia's economy minister after the previous one was reportedly detained for corruption last month.

One of more than 300 rounded up for questioning, some of those arrested were reportedly held in a luxury hotel in Riyadh, including several members of the Saudi royal family.

"Nobody, whether a prince or a minister or a businessman, is above the law," Tuwaijri said.

However, some critics have accused the Crown Prince of using the corruption crackdown as a way to sideline or silence his rivals.

"Does he need that? You think he needs that?" Tuwaijri responded when the question was put to him. "He's the most popular leader we come across in our history," he said.

That might be true, Williams reports, but freedom of speech doesn't exist in Saudi Arabia, and criticizing the crown prince would be downright dangerous. It's only in London, England that Saudi dissident Ghanem al-Dosari dares to make videos satirizing the Saudi government.

And al-Dosari says corruption in Saudi Arabia is much bigger than the current clampdown, Williams reports.

"Speaking up your mind, this is a crime in Saudi Arabia. People has disappeared and been charged for tweets," al-Dosari told CBS News.