Too costly for common sense
It appears that the Plarium designers planned on making the upgrade sketch levels of the infirmary a very valuable benefit since they priced it ridiculously high. Maybe it was supposed to raise the free revival rate of defense units to 40 or 50%? As implemented, it raises the free revival rate of OFFENSIVE UNITS ONLY to 35%. I think I have lost a total of 11 offensive units defending my city in the last 3 months! I understand that raising the % of the free revived defenders could imbalance the game but pricing a useless upgrade at 700+ sketches is ludicrous.
The awards for upgrading the infirmary should include a dunce cap.
Change the benefit to be commensurate with the cost or remove the upgrade sketch requirement.