Firstly, they overcharge for old films that are 2/3 decades old. For example, I just paid £6.99 for Robocop in SD. I really wanted to watch the film because its one of my all time favorites and I hadn't seen it in ages. But the film I am sure is shown on TV now and then because its old and am not really sure how iTunes can justify charging £6.99. I could understand £4.99 for such and old film and £1.50 for rental (maybe £1.99).
Also, another thing I find is that sometmes I download apps on two different iPads and, despite stating that you won't be charged when you download the second time, I find myself charged again each time. I then have to go through the trouble of getting a refund.