There are 10000m^2 in each hectare, so 3 hectares contains 3*10000 = 30000m^2 of land
30000m^2 is divided among 8 sons so each son will get 30000/8 = <<30000/8=3750>>3750m^2
In every 3750m^2, there are 3750/750 = <<3750/750=5>>5 portions of 750m^2 areas of land
Each son can make 5*$500 = $<<5*500=2500>>2500 every 3 months from cultivating their share
In one year there are 12 months so each son can make $2500 up to 12/3 = <<12/3=4>>4 times in a year
Each son can make a total of $2500*4 = $<<2500*4=10000>>10000 in a year
#### 10000