I wonder how much the fare discrepancy has to do with things? £3.80 all day on Stagecoach, but £6.20 on GNE? They're also over £1 cheaper for under 18s.
No idea how much a return is from say Boldon to Newcastle via GNE, but I'd be surprised if it's cheaper than £3.80.
Perhaps some Bargain Bus style competition is called for?