You can usually figure it out just wondering round the queues. Everyone I've met has done a "sketch" for free - although I think this would fall into the "little doodle" catagory as TIm Sale describes it.
Yeah, I usually go for the little doodle, but they still put time & effort into them, I can't say who though but at least years Though Bubble I got one from someone who usually charges, but there wasn't a sign up saying prices like most have, felt slightly guilty...