S3 miner was 0.58. 6 of those (2.8 Th/s) comes in at the same price for way more hashes.
Would it not cost more in electricity to run 5 x S3's than an S4?
Some questions that will help
1/ What would be the total cost of 4 or 5 stock S3's INCLUDING PSUs
2/ Can the S4 be overclocked
3/ What is the power efficiency at the wall