The sad truth is even buying 3 S3's at the above good price will not work out very well.
1350 Ghs currently generates around $200 per month (presuming zero downtime).
Take off the hosting fee and you will make around $100 per month.
So you will have to wait over 6 months for the miners to have paid for themselves.
With difficulty rises I reckon in 3 months they will be redundant.
Depressing for us small miners.
I think the mining will be still profitable, but the profit each miner can bring will become fewer and fewer. Maybe you need 6 even 8 month to reach ROI. However, it is still a high profit investment compared to the traditional business (usually need 12-36 month to achieve ROI).