Travis Scott's Late Coachella Set Cost Festival Organizer Goldenvoice $20K

1:37 PM PT -- A source familiar with the situation tells TMZ ... Green Day was running 15 minutes behind due to the fireworks debacle during Green Day's set. In turn, this caused Travis Scott's set to begin 5 minutes late. He had been at the festival for hours before going on.

Travis Scott's carefully curated Cactus Jack-themed Coachella didn't come without a price ... the hip hop headliner cost the festival's organizer $20,000 for squeezing out a few extra minutes!!!

A rep for the city of Indio tells TMZ Hip Hop that Goldenvoice will be charged $20,000 for one night of missing the curfew timeline, on Saturday, April 12, when Travis was on center stage.

It was the only fine issued for Goldenvoice across both Coachella weekends and Stagecoach festival, which went down on April 25 - 27.

City of Indio officials established the fines as part of its contractual agreement with Goldenvoice ... which outlines a daily penalty of $20,000 for the first 5 minutes past curfew, with an additional $1,000 added to every tardy minute after.

Coachella Festival and Indio initiated their existing contract in 2013, which runs through 2050 ... a move to give curfews more wiggle room than in past agreements.

The previous contract called for a midnight curfew on Fridays and Saturdays, and an 11 PM curfew on Sundays.

We're told the fines are collected for Indio's General Fund, which aids the city's operating costs, including public works and the police and fire departments.

The rap megastar wasn't slouching onstage ... he started his set at 11:30 PM and premiered two new tracks, "Dumb" and "Kick Out" that could very well pop up on his upcoming label compilation "Jackboys 2" very soon.