Several things about it are wrong. First, the assumption that promoters lost money on the tour. We don't know that. We can't know that. And if true, I doubt that it is true in more than a handful of markets they played in.
Second, even if your assumption could somehow be proven true, the model you proposed is too simplistic. It does not follow that a given promoter who broke even or lost on one tour is going to refuse to book the band on the next tour. That isn't how it works. If the losses are big enough, and if they repeat, yeah, maybe. But by itself, on a single tour, most promoters won't do that. If they cut too many big enough acts prematurely, word gets around the industry, and people stop working with them (except maybe in those rare markets where they are the only fish in the pond and have a stranglehold over that market such that you HAVE TO work with them).
Also...well, actually, forget the "also." There are a LOT of "also's" (variables) in the equation, many of which I don't even know. And that, again, is the problem with your argument. It is based on false assumptions, and it is too simplistic and doesn't take into account the many variables that are in place.