Armor is a one time expense, that's the thing. But more men is a no time expense unless you are at war. This is before the establishment of (modern) standing ar

Armor is a one time expense, that's the thing. But more men is a no time expense unless you are at war. This is before the establishment of (modern) standing armies, and the occasional armored units victorious over larger unarmored ones were the closest thing to an exception. The initial decline of the knight was perhaps less about firearms than about pikeman tactics (tercio and all that) with the various revivals of heavy cavalry mentioned, e.g. under Gustavus Adolphus, being merely reactions to shifts in the balance between pike and shot. When it's pike and shot vs pike and shot they will eventually try to outbid each other in focus on shot, until they become vulnerable again to the heavy cavalry charge that had been deemed obsoleted by pike.