Seems he was offered the chance to repay the difference, he decided not to hence the ban the same length that he has been getting away with it. Its a risk you take and seems a fair outcome to me.
The thing is he is being punished for what is essentially the clubs's own fault. OK, so he has got away with it for a few years. The club should have monitored the system better than shouldn't they.
The sensible thing for the club to have done would be to say "OK, you've got away with it, we should have been more diligent, we are on the ball now and you won't be able to get away with it again from now on. You either start paying full price or you don't come".
If it was in a shop and someone had purchased something that was marked up at the wrong price and the shop realised at a later date, they can't ask for the money retrospectively, it is the companies own fault! They should have been more alert to the situation.
Instead of this, the Albion have lost yet another supporter. Like I've said before, when the Premier League/Sky T.V. bubble bursts, we will need these supporters we are now all too easily tossing to one side.