Folks! Regarding the price. It does not correspond to the strength of level 7 units, because level 7 monsters will be bought out anyway (otherwise you won't last in a serious battle) regardless of their price, and this is how balance is fixed. The prices of creatures in all towns need to be at least roughly the same.
I calculated the weekly growth cost for different towns assuming all buildings are built:
Haven - 29590
Dwarf - 29780
Dungeon - 30350
Necropolis - 30650
Inferno - 30814
Academy - 31180
Sylvan - 31300
Thus, Academy is the only town that can pay for itself (taking the Treasury into account).