Julia Roberts was able to break the glass ceiling for A-list female movie stars only in 2000 when she commanded $20 million for the biographical legal drama 'Erin Brockovich', reports 'Variety'.

Until then, no woman actor had been getting as much pay as their male counterparts such as Tom Cruise or Tom Hanks, who ruled the 1990s box office alongside Roberts.

At Saturday's A+E Networks and History Channel's History Talks in Washington D.C., moderator Gayle King (co-moderator 'CBS Mornings' and editor-at-large 'O, The Oprah Magazine') asked Roberts about the negotiation tactics she employed to gain equal pay.

"I didn't feel so boxish about it, but I felt like, 'Come on'," Roberts said. "Which is my nature -- not to be all up-in-arms about something, but to say, 'Let's get real. Let's be fair'."

Roberts acknowledged, according to 'Variety', that she'd earned her paycheck, having carried such culture-defining hits as 'Pretty Woman', 'Notting Hill' and 'My Best Friend's Wedding'.

"When I'm working, I work very hard," Roberts said. "I'm ready. I'm on time. I'm prepared. I'm happy. I'm all-in. So, show me the money," Roberts said.

During their conversation, Roberts and King also discussed the challenges of speaking out. Often for women, King said, "taking the high road" -- in agreements about salary among other things -- means "shutting up". But Roberts maintained she was never worried about getting penalised for standing up for herself.