It will come down to the business case that can be presented to Treasury. The CrossCountry operation will always require a certain allocation of subsidy. More capacity means higher lease payments. It seems unlikely that there would be any desire to reduce the revenue yield per passenger so that additional capacity would need to be filled at current prices to be anywhere near viable.
If it needs subsidy, and how much is partly arbitrary or an accounting anomaly (depends on if other operators serve routes too, and which operator sets the fares).
If you take journeys between say Manchester or Liverpool and Bristol (3rd, 4th, 8th largest English cities) then could take a XC priced fare via Birmingham, or a TfW fare via Hereford or an Avanti+GWR via London.
There is not a lot of correlation between quality (comfort), speed (duration) and price. XC might be quickest, but often most squashed, and if unlucky to get a 4car voyager, might not get a seat either. And catering is very unreliable too (sometimes near end of journey, or static as aisles are busy)
XC has cut back routes, you can't use it to visit tourist cities like Bath, Chester or Cambridge, it doesn't serve any major airports (ok, it does serve some smaller ones like Southampton or Birmingham). At times it feels like XC is more an outer suburban service around Birmingham than a comfortable quick way to get from one side of the country to another. Is it trying to serve long distance travellers or Brum commuters. If it is the latter then yes it will need subsidy.
If it is trying to link large provincial business centres like Leeds, Manchester, Bristol etc then it doesn't do it very quickly, and why apart from Torbay does it seem to not quite reach many UK holiday destinations. It needs trains that do regional sprints, and if that means not stopping for 50+ miles both sides of Birmingham then that is market it should aim at, and get trains that are comfortable for 3+ hour journeys, not designed to call at stations every few minutes doing commuter services