The total pay per employee in a day is 12*10 = $<<12*10=120>>120
An employee works for 5*4 = <<5*4=20>>20 days in a month.
The total amount of money paid to each employee monthly is 20*120 = $<<20*120=2400>>2400
When the number of employees increased to 500+200 = <<500+200=700>>700 after the new hires in August.
The company pays a total of 700*2400 = $<<700*2400=1680000>>1680000 per month to its employees
#### 1680000