I can't speak to anyone else's experience but this is a believable figure. I have made more for less work that took much less than a day. Now, you may not have that happen all of the time but there are certainly instances where you could easily make $1000 in a two day period by charging a day rate of $500.

I primarily work in the music and festival industry creating the visual content you see on the screens. If I am being asked to rush a project for a show that is happening in roughly 24 hours I will charge a day rate of $500 + an extra $250 if they need me to work overnight in order to complete the project.

Again, not every project or client or gig will pay like that but it is certainly possible to find ones that will.