Should never be allowed to charge over face value
I think it should be done on a fixed price system. So whatever your season ticket is divided by 19+plus a sensible admin fee. Maybe a pound each from buyer and seller. There should also be an option for an auction for pre chosen "major" games (Derby, united, city etc) with any profit over the set price going to club charities. I know that last bit would still irk some as it prices some people out. My thinking tho is if you stop the opportunity for flagrant profiteering there will be more matchday tickets or even season tickets available direct from the club at affordable prices.