So, I'm at wave 50 and I'm still 35 upgrades behind to the famous "get all upgrades". And I have already upgraded the backpack to 10. I'm making around 5k and 6k per wave except on boss waves that I make almost 7k. Not to mention that when I fail a wave, I make around 3k. I'll probably post again once I finish all upgrades. Wish me luck.