While I get that the Upgrade features are meant to help and add a nice, strategic edge, the amount of points they cost do not reflect much in changes. I would suggest maybe lowering the starting costs of some base upgrades to around 1500 points instead of 3000 and work your way up as they get bigger, as most of the time, unless you’re lucky, you earn around 5k-ish a wave.
I would also like to argue that certain weapons, like the Egon, RPG, and Laser Rifle spawn very very rarely, while weapons like the sledgehammer, katana, and both Guitars are exceedingly common. I feel that the tougher some Zombies are, the better the weapons they spawn (like the red demon zombies should have a better chance of spawning a rarer wep when they die, or maybe just even out the chances some, as each weapon is fun and unique, but no one wants 3 sledgehammers in a row.)