Haim fired their agent after learning they had received 10 times less than a male artist performing at the same festival.
The 'If I Could Change Your Mind' hitmakers - comprised of sisters Danielle, Alana and Este Haim - were horrified to find out how much more the next artist up on the bill at the unnamed event was receiving, especially as they initially "didn't think twice" about their low fee because it was explained as being a beneficial promotional opportunity.
Danielle explained: "We had been told that our fee was very low because you played at the festival in the hope you'd get played on the radio.
"We didn't think twice about it, but we later found out that someone was getting paid 10 times more than us. And because of that we fired our agent."
The sisters are still furious about the incident and branded the inequality "f**ked up".
Alana fumed to Grazia magazine: "That's why I love my sisters so much. I trust them with my f***ing life. We're all in this together.
"But it's scary out there and it's f***ed up. It's f***ed up not even to be paid half the same amount. But to be paid a tenth of that amount of money? It was insane."
Haim have encountered sexism a lot in their careers and find it frustrating when their musical ability is written off just because they are female.
Alana said: "What was really scary to us was feeling like if we acted a certain way, people would think we didn't play our own instruments.
"I still get so many people asking me, 'So who really writes your songs?'
"A lot of people automatically accept the fact that an all-male band writes their own songs, but when they see an all-woman band, they're like, 'Oh there must be a man behind it, fuelling their fire.' "
Tagged in HAIM