GC have made a bit of a mistake with their pricing, IMO, as they have priced the Sunderland-London GC only saver at £6.10 MORE than the cost of the Any Permitted saver, for railcard holders. That means that anyone who holds a railcard is going to purchase the Any Permitted ticket, and as a result NatEx will get the majority of the income from all railcard holders travelling on GC (thanks to ORCATS). I think this must have been an oversight by whoever set the prices!
A way round it would be to offer, say, 15% discount to railcard holders, putting the fare at £58.65 which may just be enough of a discount to tempt people to go for the GC-only fare. This would give GC £58.65 of revenue from railcard discounted tickets rather than the much smaller amount they will recieve if railcard holders are only given discounts on the Any Permitted fares. If they do not do this, then it's GC's loss.