Do you know how many of those supersaver tickets are available? On the website for a normal ticket, they automatically seem to include some sort of half priced discount for locals.
I'll ask my contact, but I suspect it's the usual low-cost pricing, so rather than a certain number of one type of ticket (supersaver) being available, there will be tickets available at different prices - this is from their FAQs
Why are different prices offered for the same route?
The prices depend on the capacity and popularity of the connections concerned.