I think it's more appropriate to look at the funding per passenger km given sleeper journeys and ticket costs are considerably higher than for all the other TOCs.
Using that metric, it's the 5th most expensive.
£ per km
0.26 Northern
0.26 Wales & Borders
0.21 Scotrail
0.19 Merseyrail Electrics
0.16 Caledonian Sleeper
Fair enough.
In which case we should compare to the other pure long distance TOCs: West Coast at 1p/pax km, and East Coast at a negative subsidy (ie premium) of 2p/pax km.
So 16 times worse than the next closest.