Good patience waiting for this much money to spam purple units. :D You can also win by sending enough fast units which also doesnt decrease your income.
How long did you wait to get enough money without sending enough units to decrease lives?
Viewing post in Tower offense jam comments
At first I was waiting a few seconds to spam the normal units. Then, once I had enough money I spammed the fast units. This was very quick as every time I was putting like 10 fast units, I was getting an insane amount of money. I did this thing like 5 or 6 times until I started spamming the high hp ones. At the end every 5 seconds I was losing so much money that I went in negative :)