Sen. Bernie Sanders campaign takes aim at Pete Buttigieg over ‘wine cave’ fundraiser Tickets to the event started at $500 to attend.

Following a Pete Buttigieg fundraiser last weekend that drew widespread attention for its unique and opulent setting, the campaign of Sen. Bernie Sanders ramped-up attacks on the South Bend, Indiana mayor Monday and launched an online fundraising effort of their own that drew inspiration from the event.

In an email to supporters Monday evening, Sanders’ campaign manager Faiz Shakir described the Buttigieg event as having taken place in a “wine cave,” and estimated that the mayor could have brought in as much as $100,000 via the dinner, before encouraging those backing Sanders to contribute small amounts in order to match the total.

The pitch followed an afternoon of social media ribbing by a number of Sanders staffers who shared their dismay at the event and expressed a view — frequently espoused by the senator himself — that such private fundraisers result in wealthy donors gaining undue influence over candidates. Sanders’ presidential campaign does not hold private high-dollar fundraisers, opting instead to rely on grassroots donors and infrequent low-dollar events with tickets open to the public.

“The senator doesn’t have fundraisers in wine cellars,” said former Ohio state senator Nina Turner, a campaign surrogate, at a Sanders event in Rancho Mirage, California Monday.

“I do not spend my time, not one minute of one day in this campaign going to some wealthy person's home and sitting down with other millionaires and walking out with a few hundred thousand dollars, never did that,” Sanders told a Cedar Rapids, Iowa crowd a week ago as pressure mounted on Buttigieg to open his private fundraisers to reporters.

ABC News has reached out to the Buttigieg campaign for comment about the fundraiser.

‪Buttigieg’s event was held at Hall Wines in Rutherford, California on Sunday night, just outside of Napa. Tickets started at $500 to attend, $1,000 to receive a photo with Buttigieg, and a $2,800 contribution gave attendees access to a dinner with the mayor.

The media was not given access to the private dinner, only allowed in during remarks Buttigieg gave in a separate event space prior where he also took several questions from supporters. Photos from the dinner show an ornate brick room furnished with an expansive chandelier.

After receiving criticism and pressure from Massachusetts Sen. Elizabeth Warren to open his private fundraisers to press, Buttigieg made the decision to open his events last week. The mayor also released a list of his bundlers who have raised at least $25,000 for the campaign.

Buttigieg has defended holding high-dollar fundraisers. Asked by ABC News’ Rachel Scott in Pittsburgh on Saturday, the mayor said his campaign is still a grassroots organization with an average contribution of $32.

“We also need to make sure that we are bringing all of the resources that we can to this struggle," he said. "And when somebody makes a contribution to my campaign, I may agree or disagree with them on one issue or another issue. I will make one promise to them in return. And the promises that I will take that contribution and use it to defeat Donald Trump.”

Monday evening, following Shakir’s email solicitation for donations, another fundraising site began circulate on social media — a website, referring to "wine cave," purchased by the Sanders campaign that redirects to their fundraising page.

ABC News' Averi Harper and Beatrice Peterson contributed to this report.