How much do you charge to speak on stage?

I'm an early stage speaker. I've spoken on stage a number of times (https://onstage.ai/speakers/br). I like to qualify decisions I make in life using data, and I'm struggling to find case studies and data points to work out what the normalised transition is from not charging to speak at conferences and events, to charging a speaker fee any time on stage.

What do you charge to speak on stage? How did you make that transition to charging a speaker fee for speaking onstage?

Disclosure: I'm the Founder of https://onstage.ai - I built it last year because, short of building your own website, free/low-cost professional looking solutions for non-professional speakers were largely missing from the market. It's still pretty early stage - any/all feedback is welcomed :)