One thing I have been thinking... in eleven incarnations of the shopping task, there have been numerous attempts to barter prices down, but not once have I ever seen anyone ask on the phone what the price would be. To me, on a task about spending as little as you can, this would seem to be so obvious it seems remarkable that apparently no one has ever thought to do that. Which makes me think, are they banned? I can't see why they would be other than to make the task unnecessarily harder, but it's the only thing I can think of.