Fun game, but on my not-very-good PC the game slows down considerably during the late game.
Once everything is maxed, I can buy everything I want in 20 seconds. The next 10 seconds earns me 250k. From there the game slows and my final 12 seconds earns me 100k.
I should be able to get a high score of around 2.5M, but I can only manage 1.6M due to slowdown.
But if I buy everything then scroll down to the messages for two minutes, I can almost hit the expected high score.
Also, the Max Workers Speed Incr Coin upgrade increases the stat by 4 with the first purchase. Four more purchases are required to earn the next upgrade. Maybe changing the cost from 40 to 160 after the first upgrade will stop players thinking that the button is broken.