I am not disagreeing with you with regards laundering of fake coins, 90p in the pound is indeed a resaonable return, I was not aware that the machines had already proven successful with regards laundering in this regard – begs the question why the producers bother putting them into circulation, just dump them straight into one of these machines for a suitable voucher.
Although one has to question the return on investment for those counterfeiting £1 coins in the first place, you must need tens of thousands of them to just cover the equipment and manpower costs of producing them, and then you have to get them into circulation. £20 notes on the other hand, much faster ROI, but more people will bother to check them for being genuine.
However with regards processing my own non fake coins, I would prefer to receive all of the funds, rather than be subject to an admin fee.