I really want to get into the mining game at an extremely low cost (Due to bitcoin price rising drastically over the past month or so) should I buy an S4 or should I buy something a little more efficient (Power Cost is almost 10 cents per kilowatt)
I recommend to replacing the S4 that you have, the cost of electricity is very high. In addition, the difficulty level will also increase and the result mining will continue go down. If you are serious for mining, better use S7 or S9.