@Averixus I don't think those numbers prove that there's anything wrong here.
If there were no "revenue protection" at all, some people who now pay wouldn't pay. To discover whether "revenue protection" is paying its way, you need to compare the cost of "revenue protection" with _what people are paying that they otherwise wouldn't_ as well as the fines and penalty fares.
Imagine a world where everyone cheats if there's no "revenue protection" but some measure that only costs £50k/year makes everyone comply. (Of course this isn't the real world.) In that case, _obviously_ you want to pay the £50k/year, but an FOI request like yours would say: "They pay £50k/year. They earn _zero_ from ticket fines and penalty fares."
So in this imaginary world, "revenue protection" is tremendous value but looks awful by the "fines versus cost" metric.
Back in the real world, I don't know how much cheating they prevent with their "revenue protection", but I bet it isn't zero. Maybe it's more than £800k/year, maybe not. But that's the figure that matters, not what they're getting back in fines.