I know the previous incarnation of DOR prior to Virgin taking over the ECML was returning a lot of cash to the treasury
My understanding was that GNER returned “surplus” to the treasury, NXEC returned “surplus” to the treasury, VTEC’s contract promised to return “surplus” to the treasury (albeit they were stopped part way through the franchise duration, as were National Express)
franchises generally tended to promise higher returns in the the second half of the agreed period, normally the initial years were spent investing in new/additional trains, and therefore the TOC was in healthier position to return surplus in the later years (or, to be blunt - spend your money on new trains and expansion in the early years, use the increased revenue to return more £££ to the government in the later years) - the same applies to most of the subsidised franchises, where the subsidy was intended to reduce over the duration of the contract
Of course, a cynic would say that some franchises were set up like this to give an incentive to walk away part way through - e.g. First had the Great Western franchise with the option of a two year extension after the initial period, but declined to take this up, presumably in part because the onerous terms that came with the extension period weren’t particularly attractive
There was criticism of just how ambitious Stagecoach were promising to be in terms of the surplus that they said they’d return, but the government were happy with the numbers so obviously expected Souter’s company to pay the surplus that has been agreed - presumably there’d similarly have been criticism of the winning bidder if they had only offered to return a tiny amount to the treasury - people who were against privatisation would find any excuse to moan
However it’s important to note that the Government controlled “East Coast” and the current Government controlled LNER didn’t promise any specific level of surplus, so there’s no benchmark. Yes, they returned money to the treasury, but even Trotters Independent Traders would make some surplus from running this lucrative line - its a lot harder when there’s an amount that you *have* to return each year (and financial Penalties for failing to do so) - the government controlled operators are playing on a much easier setting than the tougher terms that they expected Sea Containers etc to comply with