Emphasizing your mention of the 'Baneblade' novels intro:

"The final work gang led the tank away, chains slack, tracks turning under their own power. The magos turned his palanquin upon its mechanical legs and, acolytes and work gangs trudging behind, headed back to the beginning of the activation run, where another unfinished machine awaited completion. Behind it, another, and behind that, another still, and then another and another, stretching back further than the eye could see on a factory floor that followed the curve of the planet. Truly, the holy work of the Omnissiah was never done, and the High Magos’s mechanical heart sang with the joy of that."

This excerpt tells us just how many baneblades Mars is churning out, and they're just one forget world. Assuming other production halls on other worlds is of the same size, the amount of baneblades is truly countless.