The Writers Guild strike passed the three-week mark on Tuesday, as a large rally dubbed #RallyAtTheRock took place outside NBCUniversal headquarters and featured stars like Mark Ruffalo, Busy Phillips, John Leguizamo and Kal Penn.

Even more celebrities, including SNL cast member Sarah Sherman and comedian Jordan Klepper, filled the picket lines and were joined by the Teamsters union, SAG-AFTRA, IATSE, Broadway performers and many more.

During the rally, the WGA continued to lean on financial data it published last week, in a letter signed by the WGA Negotiating Committee and distributed to its members.

Titled “The Cost of Settling,” the letter makes the argument that “the studios are risking significant continued disruption in the coming weeks and months that would far outweigh the costs of settling.”

The letter estimates that the changes in WGA’s proposal would cost the studios a total of $429 million across the industry — a number that pales in comparison to the tens (or sometimes hundreds) of billions of dollars the studios rake in each year.

Additionally, the WGA estimates that California is losing $30 million per day on lost output from the strike.

The numbers are based on the Milken Institute’s estimate that the 2007-08 Writers Guild strike cost an estimated $2.1 billion in lost output from Q4 2007 to the end of 2008, with adjustments for inflation.

So far, the three weeks of the current strike have resulted in an estimated loss of $840 million in economic output, according to a WGA source who spoke with the Daily News.

However, it’s not clear if the studios are quite feeling the heat yet. One studio exec told Deadline the statistics in the letter are “baseless and just made up to gin up their membership and make for provocative headlines.”

At the rally Tuesday, celebrity speakers took turns roasting studio executives, in particular Warner Bros. Discovery CEO David Zaslav, who was recently booed during his commencement speech at his alma mater, Boston University.

“Girls5eva” star Busy Phillips made a point to call out Zaslav, saying he “sucks so bad, he made a bunch of shouting 20-somethings from Boston sound sensible.”

Actresses Cynthia Nixon and Ilana Glazer, former Senator Al Franken and writer Tony Kushner also spoke during the event.