"Given the average earnings of around £25K, paying back £7 a week means that the government is only getting £11K back over 30 years and writing off the rest of the debt."

All based of course on the idiotic premise that your earnings remain static for the 30 years that you are referring to, which of course they will not.

For those entering the job marker the differential in potential earning power between someone with a degree and someone who has not is estimated as being somewhere between £160,000 and £400,000 over the course of their working lives.