http://www.saintsfc.co.uk/news/article/arsenal-ticketing-information-1128297.aspx
TBF Colin, this was one of their clearer and logical decisions. People were buying tickets for the cheaper games, such as Barnsley and then returning them, so as they could claim a ticket for Liverpool/Man U. They decided that the Stoke price would lead to more.
They listed the games that counted.