They give money for the destruction of mobs, but who will wait for their spawn time if you can make an automated farm? That's right, nobody! So you have created a farm where mobs spawn, they die, and you make a profit. You don't even need to dirty your hands, you just need to spawn mobs, relax and watch the automated process.
There are only 2 buttons in the game: - Spawn — You produce the 1st mob, which will bring money as long as it is alive. However, you cannot create more mobs if you have reached the limit. - Improve - Improving mobs leads to a rise in the price of Spawn, but in return you get even more profit