Factory Idle
Also it's important to note (at least for noob like me), that Money is Double * 1 rounded.
The other issue - is speedhack.
In normal mode x20 is realy ok. It gives 100-120 ticks/sec.
X50 may seem better (100-300 ticks/sec), but lag is significant.
If you want even more, than you should enable "Fast" mode (with unlimited bonus ticks). The best performance in this case is 200-450 ticks/sec with x2 speedhack.