150 Mhs gets you roughly 3 USD per day, electricity cost = 0,1 USD/kwh , 0,75 ( 750 watt ) x 24 x 0,1 = 1,8 USD electricity cost , 3-1,8= 1,2 USD profit. Is it sensible to build a mining rig with this conditions? Maybe with second hand parts, definetaly not with brand new equipment. Is it sensible to continiue mining with your existing rig? Yes
Not everywhere the electric cost is 0.1$ per kWh. Maybe OP is living somewhere where the cost is 0.15$ per kWh.