I don't pretend to understand the vast complexity of their fare structure, but XC aren't green when it comes to pricing advances. Perhaps it all comes of much better usage data and their whole 'realtime reservations' thing? I dunno. In theory, 'price discrimination' - which is what selling Advance Tickets is (selling the same travel but discriminating by the time you buy the ticket), does two things. The first is obvious; it ensures that those willing to pay the most do so i.e. they buy late and they pay more. This is sometimes called 'appropriation of consumer surplus'. The second thing it does is sell some tickets cheaper than they would be sold if every ticket were sold at the same 'equilibrium' price i.e. you buy 3 months in advance and get a really cheap ticket. Many of the people who buy those would not have chosen to travel at all if they had had to pay the equilibrium price, so the market has been widened. Both of these effects work together to increase revenue, and the idea is that you try to charge each person as much as they are willing to pay, but still keep their custom. Therefore the more accurate data you have about who your passengers are, when they want to travel and where, the better the APs you can make to cater for this. Add in the uniquely odd factor the rail industry has in that revenue from walk-ups (assuming these are the most expensive tickets) is shared and the fact that if you can get people using the XC website you don't even have to pay commission and it could be a real recipe for the highest revenue per seat going.
By these tokens, I would expect XC to be making more profit per seat than some of the other TOCs out there with overly/unimaginatively/inflexibly priced advances. Shame the rolling stock isn't up to the job!