I don’t see signs stating the prices. I’m guessing that the kid on the left is giving away the lemons, since her booth is labeled “Life” and the expression says, "When life gives you lemons . . . . " Not sure what the kid with the lemonade stand is up to.
All that said, I don’t see the point to this cartoon — there’s nothing funny, clever or profound going on here. If there’s any reason for this cartoon to exist, I’m not seeing it.