Aflac CEO says through-the-roof M&A prices thwart deal prospects

"Dan, I think I can probably speak for most of your shareholders when I say I'm really excited to hear that you believe 18 times forward earnings is a too high a price," Nadel said on the call.

"From our standpoint, we can't make it work," Amos said.

Smaller deals to enhance internal growth could make sense, though they wouldn't even be a "blip on the screen" for Aflac in terms of capital, said Amos, who has preferred to use excess funds for dividends or share buybacks. The CEO cited the insurer's $100 million acquisition of Continental American Insurance Co. in 2009, a deal that helped Aflac boost group policy sales at worksites.

Aflac rose 2.2 percent to $63.72 at 10:43 a.m., the biggest intraday rise since February. The Columbus, Georgia-based insurer projected Tuesday after markets closed that full-year operating earnings per share will climb at least 4 percent on a currency-neutral basis. The company had previously said the increase could be a little as 2 percent.