Are Keeps too expensive? Especially in comparison to Bombard Towers.

The trouble I have with Keeps, and in fact towers of all sorts, is that they take stone. Even in a good game, getting more than three castles in a game is really rare for me, but having less castles than your opponent is a really good way to lose, since they can make more unique units than you.

Building even one or two towers can mean not being as likely to be able to make my third castle, which can often lose me the game.

But even worse, Keeps cost the same amount of Stone as Bombard Towers!

Bombard towers are almost always a way better choice than Keeps, because they can actually do something when ungarrisoned.

Sure, Bombard Towers cost gold instead of wood, but that doesn't really matter in the earlier parts of the Imperial Age when gold is more plentiful, and even in the later parts of the game when gold is more valuable, the stone is easily worth 5 times more than the gold, so we're looking at maybe a 20% increase in cost for a huge increase in offensive capacity!

I don't like the idea of Keeps being spammed around willy-nilly, but it would be nice if there were some point past a trush where building keeps is actually worth it.

Would it be balanced at all to reduce the stone cost for towers with each additional upgrade? Maybe down to 100 with Guard Towers, and then to 75 stone with the Keep upgrade?

That was Trushes aren't really impacted, but Keeps would at least be potentially worth building in the castle and imperial age. And most importantly, they'd at least have some advantage over building a Bombard Tower.