Let me elaborate on my "too expensive" :
The Forge is nice to have in the beginning to equip yourself quickly without losing other actions. Usually I feel that my Forge has done its duty after lets say 3 equipment pieces..after that it's nice to have but I wouldn't care much if it is lost. It's nearly not possible that an opponent can destroy a Forge quickly enough to make one really suffer...this would have to happen basically on the same turn the Forge comes out and demands quite some commitment - an alternative for the opponent would simply be to run a Forge on his own and in that way equalize the game position. The latter one being a more flexible, less committing and imho more appealing/attractive/reasonable apporach.
Anyway, to sum this up I rarely feel the urge to replace my Forge - I also think it is a questionable/debatable strategy to try to destroy it - at least it's not an auto-target.
Also, 3+ spellbook points is a lot atm for me. I have several decks that I have been playing for a long time and it causes me sleepless nights or nightmares
when I try to find the room for even 1 spellbookpoint
Friend of mine runs an Anvil Warlord with 2 Battleforges which he both casts on Turn1 - I envy him