Are you using muli? He's a money gobbler despite his deceptive 20 bucks a pop..... its actually possible to have negative income per wave if you can slow/stun the creeps enough and muli is far enough away from the entry point.
Well... Yes and no... That might explain. :D The thing is I'm using Shadow as my carry since it wasn't that good against challenges and horseman I thought I might need a second carry. So I started building Muli. The thing is, I didn't put any Hulis till 800th rounds. I only put 4 lucky pants and watched him improve. Since he doesn't attack all he did was drink and get powerful. As of 900th level I'm using Muli full time as well but... Nah.. I don't like it :D Right now it has 21549 % Crit damage 2666 % Crit chance 1000 % Damage Add The avarage damage with 2 dried cactuses, blade of darkness and a meat mallet is 71M. Or so it says. Yeah, not making it attack and building it while having the Shadow be the first carry worked. you might say. NOPE. It doesn't. The average I get is 3-5M per attack. The best attack is 18M. On the other hand my Shadow doesn't have this much crit chance or damage yet his best attack is 955M with only 4 dried cactuses. :D Yeah, I think Muli ate all my money. Why you little #$@$! :P
Maybe you missed the big message that appears every single wave after 200 telling you there's no income in endless mode?