Stocks are not cheap: Carlyle's Rubenstein

David Rubenstein: US economy in reasonable shape
David Rubenstein: US economy in reasonable shape

Billionaire private equity pro and philanthropist David Rubenstein on Monday said stock prices "are not cheap" right now, creating a tough environment for dealmakers looking for bargains.

"Companies doing deals ... they have highly priced stock and they're using that to make acquisitions. It makes it easier for them," he said—noting it's harder for PE firms. "Right now, credit is certainly available to do deals. But people, like we, do not want to pay the prices that you often have to pay."

The co-founder and co-CEO of The Carlyle Group also told CNBC's "Squawk Box" the U.S. economy is "in reasonable shape," probably growing in the 2 to 2.5 percent range for the reminder of this year. He sees the European economy as also doing "reasonably well." But China, he added, is slowing down a bit to "6.5 percent [growth] or so this year, which isn't bad given the size of that economy."

The global investment firm, with $193 billion of assets under management, is reopening an office in Silicon Valley six years after closing one. Rubenstein said Carlyle wants to be closer to the "center of technology."

"I don't think people in Silicon Valley are quaking in their boots that we're opening an office there and all of sudden all the deals will flow to us," he joked—saying Washington, D.C.-based Carlyle could stand to do more tech deals.

Carlyle was, however, a big winner in the sale of headphone maker and streaming music operator Beats to Apple for $3 billion last year. The PE firm had a $500 million stake in Beats.

Magna Carta celebrates 800th anniversary
Magna Carta celebrates 800th anniversary

Rubenstein also talked about Monday's 800th anniversary of the Magna Carta—considered the founding document of English law and civil liberties as well as an inspiration for the U.S. Constitution.

"It may well have had more impact in this country than in England," said the Carlyle boss, who bought one of 17 copies of the charter at auction for $21.3 million including fees and commissions back in 2007. It's on display at the National Archives in Washington.

Over the years, Rubenstein has also spent his money on other historic endeavors—such as donating $7.5 million to help repair the Washington Monument, after damage from a rare D.C.-area earthquake in August 2011.

"I do like to try to fix certain historic monuments and sites as a way of getting people to go visit them ... as a way of reminding people of the great, incredible freedoms we have in this country, and also some of the historic problems we've had," he said.