Arianna Huffington’s surprise gift to Jon Stewart — a convoy of shuttle buses to his “Rally to Restore Sanity” in Washington — was an even bigger surprise to the folks at the Huffington Post.

And the cost of the grand gesture — an estimated $250,000 for 100 buses for thousands of New Yorkers — is making some of Huffington Post’s finance executives wince, according to insiders.

HuffPo’s President Greg Coleman agreed that the gesture came a surprise, but denied that there was any internal tension as a result.

“Arianna has a sixth sense for promotion, for capturing lots of attention,” said Coleman in an interview with TheWrap. “We were surprised when she made that offer. She didn’t tell us. But inside the Huffington Post this does nothing to hurt our revenues.”

Coleman is working to entice sponsors to underwrite the gesture, and turn the surprise into a revenue bonus.

“What we’re working on is turning this into an opportunity. Working with largest marketers in country to sponsor this Sanity Bus Tour. This one is going to cost us some money, and we are looking at this as an opportunity.”

A spokesman for HuffPo told TheWrap that 11,000 people had already signed up for the buses as of late last week.

Read also: More Than 100,000 RSVP for Stewart, Colbert D.C. Rallies on Facebook

Huffington confirmed to TheWrap that she made the sudden decision during her Sept. 28 visit to “The Daily Show.”

“Jon and I were talking in the green room about the rally. I said, ‘Oh my God, how are those people going to get there?’ On the air I decided to make that offer, it was spontaneous, and nobody knew. My people were in the green room with me, and even they had no clue.”

To Stewart’s delight and apparent surprise, the new-media mogul pledged “as many buses as there are people to fill them” from Huffpo’s headquarters in Manhattan to the comedian’s Oct. 30 rally on the Washington Mall.

Read: Huffington Offers Free Buses From NYC to D.C. for Stewart’s Rally

"Oh my God, Arianna just Oprah'ed the buses!" Stewart said the following night. "By the way, I hope that her announcement was real and not some Huffington Post thing where it's not like actual transportation, it's just embedding a link to Greyhound. Like, I hope they're not just being bus aggregators in this situation."

"But the announcement was a “shock to the system” back at HuffPo, according to one insider, where employees were left to deal with curiosity seekers wandering by to sign up for the buses. (On the air, Huffington invited rally-goers to “just come to the Huffington Post, 560 Broadway in Soho; the bus will be there, we’ll take you with us!”)

And bean-counters wondered how much it was going to cost at a time when the company is seeking to show revenue growth and fiscal discipline.

The company was in talks to be acquired by Yahoo! — where HuffPo CEO Eric Hippeau is on the board of directors — in the spring, but those talks broke off inconclusively after the two sides could not agree on a valuation for the site.

A knowledgeable insider said there are no current talks ongoing at the portal, which is experiencing its own internal turmoil with executives leaving in droves.

Meanwhile, HuffPo spokesman Mario Ruiz says people have been signing up for the bus trip by the thousands.

“We are all super excited about it,” Ruiz told TheWrap, “along with over 11,000 who have signed up. Everyone from the company’s been ‘on board’ from the get-go, and we can’t wait for Oct. 30.”

Said Coleman: "This one costs some money. But my head is down. Arianna is my partner. We’re dialling a lot of people.”

Still, Coleman won't be anxious for his partner to appear on The Colbert Report anytime soon — host Stephen Colbert has challenged Arianna to provide buses to his rival Keep Fear Alive rally on the same day as Stewart's.