Anything with any mention of prices on a van, looks unprofessional to me. It sends out signals of cheapness no matter how put and gives the impression that that's the emphasis rather than the quality of work.
I dont agree that minimalistic signing is the best way to go either. Sure a van with a lot of text cannot be read as it whizzes by, but it does get noticed, so the trick is to mix big text to grab attention and smaller text to tell the story. A van should be a billboard that people can read when it is parked up, not on the move.
My van is signed that way and I am always catching people reading the text, it does work!
Dave.