San Francisco is covered with billboards for Brex, a startup that provides corporate credit cardsto startups.Plenty of startups find opportunities to brag about spending so little money on marketing, butBrex cofounder and CEO Henrique Dubugras says the ads were worth every penny.Brex, which has raised a total of $57 million in funding from Peter Thiel and Y Combinator, spent only $300,000 on the ads plastered on bus stops, buildings, and billboards.In San Francisco, there are few places to escape them.Jet-black billboards advertising Brex, a startup that offers the first corporate card for startups, loom over the streets and sidewalks.When you realize you are living in an alternative dimension, not the real US. Bus stop ad in SF on way to #GoogleNext18. Brex, the card for when you don't know if or when you will get your next funding round. pic.twitter.com/6xeZ0BYq03' Phil Edholm (@PEdholm) July 25, 2018The startup appears to have gone all-in on marketing, with posters on bus stops, sides of buildings, and billboards concentrated in the South of Market neighborhood, which is home to many startups.In a Thursday night fireside chat with Business Insider and Brex cofounder and CEO Henrique Dubugras, a member of the audience asked Dubugras to explain his thinking behind "taking over San Francisco" with billboards and reveal how much the campaign cost. ...Sponsored: If you enjoyed reading this story so far,why don't you join Business Insider PRIME'Business Insider provides visitors from MSN with a special offer. Simply click here to claim your deal and get access to all exclusive Business Insider PRIME benefits.SEE ALSO:A buzzy startup raised $57 million from Peter Thiel and Y Combinator using these 19 slidesJoin the conversation about this storyNOW WATCH: We drove a brand-new Tesla Model X from San Francisco to New York ' here's what happened Click here to read full news..