Yeah so after trying every level, I'm certain the dev hasn't even tested to see if the balancing works. There's no way anyone can feasibly complete this, the enemies have too much health or move way too quickly or have some special ability that makes it essentially impossible. The money needed even getting the cheapest weapon requires roughly two waves to acquire, and it isn't nearly powerful enough to get through the next X waves to get the next weapon, let alone money for opening doors or drugs for healing or whatever else the drugs do.
EDIT: Since people keep quoting and liking this post, I'll just say that there was some serious balance passes since I made this. The levels are still difficult, but they seem possible now.