Thanks a lot for the feedback. I'm glad that somebody got to experience the lack of social distancing leading to things getting out of control!
When the cash was working, I had hoped that starting off with a small amount of cash would have led to players having to make more strategic about if they were going to upgrade or build a new turret somewhere else. Perhaps if I revisited this I would put a limit on how many times a turret could be upgraded, random or semi-regular increases in enemy stats as the game goes on or other limiters such as turret ammo. I toyed with the idea that the turrets would have their own ammo and the player would have to jump in and reload it manually.