(URGENT QUESTION) How do artists formulate their talent fees?

Hii fellow artists! I'm running to you guys because this will be my first time being invited to an event and do live art (i do chibis). I was offered to be paid a talent fee and they said I should let them know what my talent fee should amount to. The issue is, I don't know the basis of my talent fee ToT

How do u (fellow artists) come up with the prices of ur talent fees? i hope anybody will respond asap please please please🥹 thank u so much, ur responses means a lot !!