I’m embarrassed to say that I’m surprised. Given the amount they stood to make and the obvious appearance of sympathy with the “Betray Us” message that would come if they gave them a deal, they couldn’t possibly have done what Bob Owens accused them of doing, I thought. But they did.

According to Abbe Serphos, director of public relations for the Times, “the open rate for an ad of that size and type is $181,692.”

A spokesman for MoveOn.org confirmed to The Post that the liberal activist group had paid only $65,000 for the ad – a reduction of more than $116,000 from the stated rate.

A Post reporter who called the Times advertising department yesterday without identifying himself was quoted a price of $167,000 for a full-page black-and-white ad on a Monday…

Citing the shared liberal bent of the group and the Times, one Republican aide on Capitol Hill speculated that it was the “family discount.”

Maybe it’s because they thought a nonprofit like MoveOn couldn’t afford to pay the full rate? Er … no, it can’t be that. Like the man says, the only obvious explanation is the family discount. Lesson learned: never underestimate the Times.

They’ve probably lost at least one reader over it. Oh well. Exit question: What kind of deal do you suppose Silky got on this?

Update: Yeah, surprise.

New York Times spokeswoman Catherine Mathis tells me that it’s Times policy to not “disclose the rate that any one advertiser pays for an ad. The rate that is charged for an ad will depend on a variety of factors including how frequently the advertiser advertises with us, the day of the week, is it color, is it black and white, what section it appears, all of those kinds of things.”…

Mathis points out that on September 11, 2007, “we published a full-page advertisement from Freedom’sWatch.org, an organization whose view is opposite of MoveOn.org.”

Freedom’s Watch spokesman Matt David, however tells me the group was charged “significantly more” than MoveOn.org for its ad. The organization says it plans to run a response to the MoveOn.org NYT ad in the Times, “and we plan to demand the same ad rate they paid,” David says.

Update: Word on the Hill from Politico is that the MoveOn was a “blunder of the highest order.” Says savvy nutroots pointman for America’s new Democratic center Matt Stoller, “I think it’s awesome. I’m glad MoveOn said it. There’s very little split in the Democrats who, I think, basically believe Petraeus is a partisan shill.”