Well it looks like supporters are to blame. According to this morning's CT who are running a quote in response to a season ticket holder wanting to return their season ticket, the blame lies with supporters who have not bought enough season tickets at full price and in cash.
The unattributed quote goes: "If you had paid full price for and cash up front for your season ticket then players wouldn't have to be sold."
Feel free to discuss this on the various City message boards.